march - arecibo observatory

The NAIC is operated by Cornell University under acooperative agreement with the National Science Foundation.

March 1998, Number 24

work taking most of the day time. SinceJanuary we have been limiting azimuthmotion to about 720° per day becauseof concerns about stresses in the azi-muth system due to the radial misalign-ment of the azimuth rails. Available re-ceiving systems were the CarriageHouse 430 MHz line-feed system, andthe 430 MHz, 1400 MHz, 2380 MHz(room temperature) and 5 GHz systemsin the Gregorian Dome. Data frompointing observations, input to a point-ing model, resulted in rms pointing er-rors at L- and S-bands of less than 7arcsecs. Radio astronomy observationshave concentrated on confirmation of

INDEX

The Upgrading Project 1Proposals & Commissioning 2

The Winter HF Campaign 3Atmospheric Sciences Highlights 3 The Coqui II Rocket Campaign 4

Radar Astronomy 5 Radio Astronomy Highlights 6

AOFTM 9Receiver Status 10L-band Filters 10

New Ionosonde Antenna 11Computing at AO 12

IRIDIUM Agreement 12One Year of AOVEF 13Comings and Goings 14

The Upgrading ProjectDon Campbell

This should be the last newsletterthat discusses construction activ-

ity related to the upgrading project forthe telescope. Over the past severalmonths we have been working on sev-eral alignment tasks which were eithernot completed by the contractor or areremedial. The shimming of the eleva-tion rails and rack gear and the align-ment of the masts and booms of thenew platform tie-down system werecompleted last October. This allowedthe platform to be lowered to close to

its focal height and for some observa-tional programs to begin. The heightalignment of the azimuth rails was com-pleted in December and preparationswere begun for the difficult and time con-suming tasks of adjusting the radii of theazimuth rails to their design value andcentering the eight azimuth trolleys. Ad-justing the radii of the azimuth rails wasfinished in mid-March and work on thecentering of the trolleys is expected tobe completed by late April.

Over the past five months the telescopehas been used for a mix of commission-ing activities and observations at nightand on week-ends, with the alignment

The Arecibo Observatory sodium resonance lidar’s laser and telescope frame the luminous cloudfrom a TMA release during the Coquí II sounding rocket campaign in February-March. See thearticle on page 4.

NAIC/AO NewsletterMarch 1998, Number 24 2

pulsar suspects from previous searchobservations, on pulsar timing, and onVLBI observation in conjunction withHALCA, the Japanese orbiting VLBIsatellite. In atmospheric sciences, therehave been a number of world day runs,observations related to the Leonid me-teor shower, an ionospheric modifica-tion campaign in January using the HFFacility and 430-MHz incoherent scat-ter radar, and an eight week series ofobservations in support of a NASArocket campaign in February andMarch. The S-band planetary radar sys-tem was used bistatically with the 70-m NASA/JPL Goldstone antenna in anattempt to detect Titan and two smallnear earth asteroids, 1997 UL and 2102Tantalus. The first monostatic obser-vation was in March, an attempt to de-tect another near earth asteroid,1988EG.

With the completion of the alignmentof the azimuth system, the telescopewill return to full operation at frequen-

cies up to S-band(2380MHz). Commis-sioning activities willdominate the schedule inMay and, hopefully,scheduled observationswill dominate it in Juneand thereafter. Opera-tional receiver systemsare expected to be thecooled 430MHz line-feed

system of the Carriage House and cooled430MHz, L-band and S-band systems inthe Dome.

The implementation of short wavelengthoperation (6 cm and shorter) is dependenton more precise focusing of the telescopeoptics via 1) dynamic control of the heightand attitude of the suspended structure us-ing the tie-down system; 2) a small cor-rection to the orientation of the Dome tobetter align the optical axis and 3) dynamiccontrol of the tertiary reflector position.The tie-down system is currently used toset the height of the suspended structureand is close to being fully operational. Itscontrol still needs to be integrated with thetelescope’s pointing system. Preparationsare underway to adjust the orientation ofthe Dome, which was designed to allowthis to be done. Dynamic control of the ter-tiary reflector is not essential for shortwavelength operation but will make the fo-cusing task much easier. Control of the ter-tiary is planned for the late summer.

Proposals & CommissioningDaniel Altschuler & John Harmon

As reviewed in the previous article,surveying of the azimuth track

and trolleys was recently completedand showed that we needed to adjustthe radial alignment of both of these,simultaneously performing somemodifications to the mounting of therails. This work is already well under-way, and the alignment of the rail iscomplete.

In addition, our initial commissioningmeasurements have shown that, whilewe are close to our design sensitivi-ties at L- and S-band, we are presentlybelow the anticipated efficiency at C-band. One factor contributing to thisis an incorrect pitch setting for the newGregorian dome. We have been inves-tigating a variety of possible fixes;these include either repositioning ofthe tertiary reflector or installation ofa modified mounting system for thedome that will allow both its pitch androll to be adjusted. It is likely that wewill implement the findings of thisstudy to improve the dome alignmentsoon, although this may be deferreduntil the summer, to allow L-band ob-serving to start in May. We also needto work on holding the focus of theGregorian more accurately constantover the full elevation range. The goodnews from recent commissioning mea-

Photographs by Tony Acevedo.

Above and left, two views of our hard working and brave maintenance crewduring the adjustment of the azimuth trolleys.


surements is that the pointing of thetelescope is already close to the designgoal of 5 arcsec.

As soon as the alignment work is com-plete, the second phase of commission-ing will commence and is expected toconsist of about 3 weeks of measure-ments with the L-band, S-band andGregorian 430-MHz receivers. Workby our staff will concentrate on mea-surements of pointing, and system per-formance, including the various back-ends and the new control software. Wehope to begin scheduled observing inlate May.

Proposals:

We received 55 proposals for the spe-cial Dec. 15, 1997 deadline and thesewere duly sent for refereeing. Refereecomments are now in. The subsequentFeb 1, 1998, deadline yielded 28 pro-posals, which have gone for referee-ing. In addition, we still have 40 ac-tive 430-MHz, line-feed, proposalspending from the Feb 1, 1997, dead-line.

A total time request of about 2600hours was received for the Dec 15 1997deadline. A similar amount of timefrom previous deadlines are also be-ing considered concurrently for sched-uling. It is our intention to start sched-uling a number of the proposals fromDec 15, 1997 and Feb1, 1997 (CH 430-MHz) deadlines as soon as possibleproviding as much lead time to observ-ers as feasible given the telescope workdetailed above. Any proposal originallysubmitted for the 430-MHz CarriageHouse feed can be moved to theGregorian 430-MHz system, if so de-sired by the proposer; no formalresubmission or notification is re-quired. After June 1, we will alsoschedule proposals from the Feb 1,1998 deadline. After Dec. 15, 1998, wewill no longer schedule the remainingFeb 1, 1997, and Dec 15, 1997, pro-posals. Feb 1, 1998, proposals will re-main active until Feb 1, 1999.

An exception to the above timetable areLong-Term Proposals, which have their

initial observations before the above cut-off dates. These can remain active for upto two years, providing a progress report issubmitted to the Observatory Director priorto 10 months after the first observations.Please take this opportunity to send us yourfeedback which will contribute to improv-ing our procedures.

Daniel R. Altschuler - Director:[email protected].

John K. Harmon - Assistant Director:[email protected].

The HF Campaign in the Winter of 1998Mike Sulzer

This January and February was the lastchance for many years to perform a

winter solar minimum HF campaign andthe first chance to do it with the upgradedHF facility. In these experiments we studythe development of large-scale density andtemperature cavities, the production of air-glow, and the thermal balance of the iono-sphere. The small ionospheric electron den-sities which occur in solar minimum win-ter allow the largest electron temperatureenhancements and thus the best conditionsfor these experiments. Both the 430 MHzradar and the HF facility performed nearlyflawlessly during the entire campaignwhich began in the second week of Janu-ary and lasted until early February. Opti-cal equipment belonging to both the obser-vatory and visitors collected data over most

of the interval.

The higher power of the upgraded HFfacility made a big difference in theseexperiments. The airglow resultsshowed the largest improvements overprevious campaigns. Large red line en-hancements occurred almost routinelywhile spectacular green line emissionsoccurred simultaneously with sporadicE. We now have remarkable green lineimages showing the striated structureswhich occur in the F region during il-lumination by the HF.

Preliminary results from these experi-ments and the ones from last summerwill be discussed in the Santa Fe iono-spheric interactions workshop whichbegins on April 19.

Atmospheric Sciences HighlightsCraig Tepley

V isitor and in-house initiated research in the atmospheric sci-

ences at Arecibo gained some momen-tum during the last few months as weramp up to full operation. There weretwo sets of World Day observationsthrough the end of 1997. The first in-vestigation took place between 20 and23 October to study the dynamic ef-fects of sub-storm related phenomenaand their influence on the ionosphereover a wide range of latitudes. The sec-ond World Day experiment, a topside

Image courtesy of Ludmilla Kagan

All-sky CCD image showing strong heater-in-duced enhancement and gravity wave struc-ture in the OI (557.7 nm) airglow emissionduring a blanketing sporadic-E event on 22January 1998.

Image courtesy of Ludmilla Kagan

All-sky CCD image showing sporadic E structurein the OI (557.7 nm) airglow emission excited withthe HF on 26 January, 1998.


ionospheric run, occurred during 2-4December, and was designed to studythe distribution of light ions, such asH+ and He+, in the plasmasphere. Forboth of these observations we operatedwith the radar beam fixed in the verti-cal direction, and only during the night.Nevertheless, radar data from both ex-periments were of high quality and arecurrently being compared with similarresults obtained from other incoherentscatter radar facilities.

During these two World Day periods,and for many additional days duringthe dark moon period in November, wealso observed several airglow emis-sions from the upper atmosphere withour optical instrumentation. The ob-servations consisted of thermosphericwind measurements by observing theDoppler shifts of the O(1D) 630.0 nmemission, intensity measurements ofO(1D) and O(1S) at 557.7 nm using ourphotometers, and spectrophotometricobservations the O

2 (0-1) and OH(6-2)

rotational bands. Analysis of O2 and

OH emissions yield the neutral tem-perature of the atmosphere near ap-proximately 95 and 85 km, respec-tively. For all of this time, the visitingCornell Imager was operated remotelyfrom Ithaca by several EE graduate stu-dents collecting interesting data onwave phenomena of the mesosphereand thermosphere.

In December, John Meriwether and hisstudent Jonathan Wrotny of ClemsonUniversity installed a narrow field-of-view photometer in the Optical Lab. Tomake up for the reduced cone angle,their instrument uses a large aperturefront-end provided by an 8-inchCassegrain telescope to increase thesensitivity. This instrument is intendedto be operated unattended making in-tensity measurements of the 630 nmoxygen line, as well as nearby OH linesfrom the Meinel 9-3 band. In Decem-ber, this mode of operation was testedand the Clemson photometer was madeready to participate in the January 1998heating campaign.

Details of the HF studies that took place

during the January heating campaign werediscussed by Mike Sulzer in a the previ-ous section. Here we note the additionaloptical support for three of the experimentsconducted by Frank Djuth (Geospace Re-search), Paul Bernhardt (Naval ResearchLab), and Bob Kerr (Scientific SolutionsInc. and Boston University). Bernhardtfielded his own imager, and, together withDjuth for two of the studies, measured theeffects on the atomic oxygen 630.0 and557.7 nm airglow due to the presence ofaccelerated electrons generated by the in-teraction of HF radio emissions with thebackground ionosphere. On a few rare oc-casions, we observed large enhancementsin the lower thermospheric “green-line”(557.7 nm) as the HF radio waves werereflected from strong sporadic layers ofionization in the vicinity of 100 km alti-tude (see images accompanying previousarticle).

For these HF experiments, we also ran theClemson photometer (as noted above), ourown photometers with high time resolutionto provide calibration to the visiting instru-ments, and our red-line Fabry-Perot inter-ferometer (FPI) to measure the neutralwinds of the thermosphere. Bob Kerr, onthe other hand, reconfigured our secondFPI to observe exospheric Hα for a fewnights in January. With Sixto González andMike Sulzer, they were looking for a sig-nature that would indicate the possible“heating” of neutral hydrogen due to reso-nant charge exchange with H+ that has in-teracted with the HF radar energy distrib-uted along the magnetic field lines at highaltitudes.

We made a big push to observe the Leonidsmeteor shower in November. Severalnights of radar and lidar time were allo-cated and additional visiting instrumenta-tion were fielded at Arecibo. JohnMathews (Penn State) and Qihou Zhou(NAIC) operated both the 430 MHz and47 MHz radars to look for signatures ofmeteor trails, while Jonathan Friedman(NAIC), Steve Collins (Cornell), and BrentGrime (Penn State) used the sodium reso-nance lidar for the same purpose. (Due tonear full moon conditions at this time, wedid not use our wider-bandwidth airglow

instruments.) While clear meteor sig-natures were observed in the radar dataat both frequencies, evidence for me-teor trails were not so conclusive in thelidar results. These require further in-spection, and Brent Grime is perform-ing this analysis as part of his Masters’thesis work.

In addition to the operation of theCornell Imager mentioned above, LyleBroadfoot, Jim Gardner, and KalynndaBerens of Arizona State brought animaging spectrograph to Arecibo toparticipate in the Leonids campaign.Due to the added convenience of moreworking space, they set up and oper-ated their spectrometer from our newLidar Lab, effectively christening theLab with a maiden set of airglow ob-servations before its actual dedication.Our lidars were not moved to the newlab in time for the Leonids observa-tions, so the prize for the first setofobservations from the lab goes to ourvisiting investigators. The Arizonagroup returned again in January toparticipate with Paul Bernhardt in hisheating experiment.

Following the Leonids campaign, webegan the big move of equipment tothe Lidar Lab. Steve Collins began towork on the alexandrite laser, whichhad suffered badly in the not-so-friendly environs of the Grease PitLaboratory. Nearly every optic showedsigns of permanent damage due to con-densation. Fortunately, the laser rodsand pump chambers had spent thoseidle months at the factory forrefabrication. By Christmas, both la-ser systems and their receivers weremoved and becoming operational.

Lowering a lidar telescope onto the new lab.


The Coqui-II Rocket CampaignCraig Tepley & Jonathan Friedman

Starting mid-February, the first setof rockets of the NASA/NSF

Coqui-II Campaign were readied forlaunch from a temporary site in VegaBaja on the north coast. Eleven rock-ets will be launched in all, and all butone will study the turbulence and ion-ization layers of the lower ionosphere.One rocket will fly through our HFbeam to study ionospheric “turbu-lence” at higher altitudes. Three launchwindows are planned, and rockets willbe launched in six separate salvos.

At the time of this writing we havecompleted the first two launch win-

dows and only four rockets remain. Thestudies addressed by the first sevenlaunches were: investigations of diffusionand turbulence near 100 km altitude, theoccurrence and development of suddenatom layers, studies of the distribution ofintermediate layers of ionization in the E-region ionosphere, and studies of iono-spheric structure due to the interaction ofthe HF radar transmissions. Four rocketsflew only instrumented payloads, whilethree released trimethyl-aluminum (TMA)which, as shown in the photo on the firstpage, forms a visible cloud as it burns incontact with the air. Photographic tomog-raphy, using strategically distributedground-based cameras, is then employedto map out the upper altitude winds.

Some 14 organizations participated inCoqui-II, including NASA, NSF, NAIC/Arecibo, the Aerospace Corporation,Clemson, Cornell, Colorado State, andUtah State Universities, the Universities ofIllinois, New Hampshire, Texas/Dallas, andPuerto Rico at Mayagüez, plus the CentreNational de la Recherche Scientifique(CNRS) in France. Portable radar and op-tical equipment were fielded throughoutPuerto Rico. The University of Illinois VHFradar, fielded by Steve Franke and ErhanKudeki, Jim Hecht’s (Aerospace) imager,and Miguel Larsen’s (Clemson) cameraswere located at the National Guard facili-ties at Camp Santiago in Salinas. At an-other National Guard site, Fort Allen inJuana Díaz, PR, Christian Hausein ofCNRS set up an HF radar to study the lowerionosphere during the launches. At theAguadilla site of the UPR-Mayagüez/NAIC MF radar, Wes Swartz fielded theCornell University Portable Radar Interfer-ometer (CUPRI). Finally, Miguel Larsenset up additional cameras at RooseveltRoads Naval Station and outside the LidarLab at Arecibo to triangulate on the TMAreleases.

At Arecibo, we operated our 430 MHz in-coherent scatter radar, Na resonance lidar,and additional optical equipment to supportCoqui-II. Both radar and lidar measure-ments were used chiefly to establish launchcriteria by examining ionospheric and neu-tral atom layer conditions, respectively. All

radar and optical observations werealso used as a diagnostic to help sortout the details of the various scienceobjectives. For example, we are try-ing to understand what triggers the sud-den occurrence of large enhancementsin thin neutral atom layers, such as so-dium or potassium, at heights whereradiative (ion-electron) recombinationprocesses are expected to be extremelyslow. Lidar scatter from these neutralspecies, radar measurements of thebackground electron concentration, aswell as its enhanced layers of ioniza-tion, radar and optical observations ofwinds (the latter through TMA orFabry-Perot 557.7 nm observations),and in-situ rocket measurements of thechemistry and energetics, all contrib-ute pieces to the puzzle.

Radar AstronomyDon Campbell

The first tests of the S-band planetary radar system were begun in

late October after the lowering of thetelescope’s suspended structure toclose to the focal height and the devel-opment of a preliminary pointingmodel giving approximately 15 arcsecpointing accuracy (at S-band). Initialmeasurements indicated a gain ofabout 8 K/Jy (72.4 db), approximately1db less than the design value but sig-nificantly higher than the 6 K/Jy of theold system. The lower than expectedgain is thought to be due to a slight(and correctable) mis-focusing sincethe gain at 1.4 GHz is close to the de-sign value. As a test of the transmitterand antenna, bistatic observations ofTitan were made on October 20-21 and28-29 and November 2 with Arecibotransmitting and the NASA/JPL 70 mGoldstone antenna being used to re-ceive the echo. Similar bistaticonservations of two small near earthasteroids, 1997 UR and 2102 Tantalus,were made on 30 October and 20 De-cember, respectively. The new trans-mitter worked well putting out between800 and 900 kW of S-band power. Un-fortunately, it suffered an arcing prob-

Photo by Jonathan Friedman

A time exposure of the launching of a testrocket prior to the March 11 launch of MikeKelley’s (Cornell) HF rocket.


lem in a klystron filament transformerduring the Tantalus observations neces-sitating removal of the klystron fromthe transmitter to repair the trans-former. No detections were obtained,which was not completely surprisingsince all three objects were very mar-ginal targets. However, the Goldstoneradar also failed to detect 1997 UR and2102 Tantalus, indicating that at leastsome of these very small near earthobjects are either smaller than deducedfrom their optical reflection propertiesor have very low density surfaces mak-ing them poor radar wavelength reflec-tors.

Over the past several months there hasbeen a significant effort to get the newplanetary radar system operational. Adual channel, cooled HEMPT front endamplifying system has been built andwas installed in early April. The phasecenters of the separate transmitter andreceiver horns are only 16 inches apartso there was considerable concernabout coupling transmitter power intothe receivers. Measurements of thecoupling gave -73 db, a very high iso-lation but not quite enough to protectagainst the 1 MW transmitter power. Aremotely controlled mechanical shut-ter to cover the mouth of the receivehorn and interlocked with thetransmitter’s RF drive signal was con-structed at NAIC’s Ithaca laboratory.The shutter provides -57 db of addi-tional isolation.

Full computer control of the system hasalways been one of the design goals.This is especially important for obser-vations of near earth asteroids or com-ets where the round trip light time isless than one minute. Automatic trans-mit/receive switching requires controlof the pointing, the turret floor tochange horns, the shutter over the re-ceive horn, the transmitter drive sig-nal, the time reference of any transmit-ter modulation signal, Doppler shift-ing of the transmitted signal or the re-ceiver local oscillator, and data acqui-sition. With the exception of final testson the new 20 MHz bandwidth radar

decoder, all of these systems have beentested and we are in the process of inte-grating their control. The next set of ob-servations are planned for May when muchof the system should be fully operational.

Radio Astronomy HighlightsKiriaki Xilouris & Chris Salter

The Arecibo telescope recovered fulltracking in early October 1997, mark-

ing the beginning of the post-upgrade re-commissioning phase. On November 7th,1997, following the establishment of sat-isfactory pointing models for both theGregorian Dome and Carriage House byNAIC staff, the first post-upgrade externalastronomy users were scheduled. Theprojects performed to date have all been inthe pulsar subfield, and have included theconfirmation of candidates found duringthe upgrade drift-scan (and other) pulsarsearches, timing measurements, and hightime resolution pulsar studies.

A number of groups have attempted con-firmation of candidates from their respec-

tive upgrade drift-scan pulsar searches.Most used the Penn State Pulsar Ma-chine (PSPM), made available as aUser Owned Public Access Instrumentby Alex Wolszczan (Penn State). ThePSPM is a 2 x 128 x 60-kHz filter-bank,and in search mode samples the dataat 80 microsec intervals. Wolszczanhimself succeeded in confirming 5 newpulsars from the PSU/NRL search (seeFig. 1). Likewise, Andrea Somer andDon Backer (Berkeley) confirmed afurther 3 objects (PSRs J0030+0454,J0711+0933, and J1312+0932) usingthe candidate list assembled by AlexZepka (Hitachi) from an analysis of thedata from the Berkeley/Cornell search.Of these objects, J0030+0454 has a4.8-millisecond rotation period (Fig.2). A further 21 candidates were also

0 20 40 60

0

light/light.0.21.pos.d.d0.n1

Period (ms) = 64.9453299999

Fig. 3: The 430-MHz pulse profile of the 65-millisecond period pulsar discovered from theCaltech intermediate-latitude search. (Cour-tesy of Stuart Anderson).

Fig. 2: The 430-MHz pulse profile of the 4.8-millisecond period pulsar, PSR J0030+0454,discovered from the Berkeley/Cornell upgradedrift search. (Courtesy Don Backer).

0 1 2 3 40

0.2

0.4

0.6

0.8

1

PHASE [ms]

Fig. 1: The 430-MHz pulse profiles of 4 of the pul-sars discovered from the PSU/NRL upgrade driftsearch. (Courtesy of Alex Wolszczan).


observed by these same observers, andanalysis is proceeding for these. In ad-dition, Xilouris (NAIC) and AndyFruchter (STScI) took data on 10 can-didates from the STScI/NAIC upgradedrift-scan search. It is estimated thatthe present total of confirmed pulsarsresulting from the upgrade drift-scansearches now stands at 67, with manymore discoveries expected over thecoming months.

The primary 430-MHz drift-scan pul-sar searches themselves received noobserving time between early Octoberand December 22nd, 1997. Neverthe-less, due to on-going upgrade-relatedengineering work, search data with thePSPM were acquired on 47 days be-tween December 22nd and March 8th,1998. Much of this data was essen-tially radio-frequency interference free.During these measurements, the Car-riage-House pointing was good to bet-ter than 30 arcsec. The upgrade

searches have nowcompleted cover-age of over 70% ofthe Arecibo sky.Stuart Andersonand Rick Jenet(Caltech) have con-firmed a bright new65-msec pulsar(Fig. 3), plus fiveslower pulsars,found from therecords of the pre-upgrade Caltech in-termediate-latitudesurvey. Also withinthe classification ofpulsar search, inthis case via a post-upgrade proposal,Xilouris used fulltracking to placestringent upper lim-its on the flux den-sity of the GemingaX-ray pulsar at 47and 430 MHz.These limits are ofespecial impor-tance in view of re-

cent claims of a detection of this object near100 MHz by Russian astronomers. Previ-ous to these measurements, the 47-MHzsystem had been completely revamped byobsevatory technicians Antonio Nolla andJosé Rosa, in collaboration with Xilouris.Finally, Jim Cordes and ZavenArzoumanian (Cornell) acquired data on 12candidates from the pre-upgrade piggy-back pulsar search using the recently com-missioned Arecibo Observatory FourierTransform Machine (AOFTM; seeAOFTM article in this issue) as backend.

Post-upgrade pulsar timing has been initi-ated by several teams, with observationsbeing undertaken both from the CarriageHouse at 430 MHz, and from the GregorianDome at 430 MHz and L-band. In Novem-ber 1997, Wolszczan timed three pulsarswhich had been regular timing targets be-fore the upgrade, finding excellent agree-ment between the measured pulse arrivaltimes and the values extrapolated from pre-upgrade ephemerides (Fig. 4). Included

among these was PSR B1257+12, thepulsar with its own planetary system.Wolszczan and Anderson found simi-lar good agreement between the newobservations and the existing ephem-eris for the 4.6-msec pulsar, PSRJ1709+23, discovered in the early daysof the PSU/NRL drift-scan search.They also confirmed the 23-day bi-nary-orbit model derived previouslyfor this object. These observers usedthe PSPM in timing mode. With itsuser-friendly interface developed byAnderson and Brian Cadwell (NRL),this machine makes for simplicity inobserving sessions, irrespective ofwhether these are local or remote.

Somer and Backer used the Arecibo-Berkeley Pulsar Processor (ABPP) torefine period parameters and determineaccurate dispersion measures for thethree newly discovered pulsars fromthe Berkeley/Cornell drift-scan search,(see above). Their preliminary conclu-sion concerning the new millisecondpulsar, J0030+0454, based on its ap-parent negative period derivative, isthat the pulsar is in a long-period bi-nary system. A recent complementaryVLA observation determinedastrometric parameters forJ0030+0454. Observations of PSRJ0631+1036 indicated that the pre-up-grade timing model is still accurate.Their observations used a combinationof the 430-MHz Carriage-House re-ceiver and 1400- and 1660-MHztunings of the L-band receiver in theGregorian dome. Although monitorand control of the telescope, receiverand ABPP are still under development,the observations were straightforward,highly successful and demonstrated theagility of the “new” telescope and as-sociated hardware for pulsar research(Fig. 5). The ABPP is a 32-channel, co-herent-dispersion-removal, integratingbackend for precision timing and po-larimetry. Channel bandwidth is se-lected based on dispersion over a rangefrom 4 MHz down to 0.125 MHz insteps of “root two”. If you are inter-ested in use of this system please con-tact Don Backer at:

Fig. 4: Pre- and post-upgrade pulsar timing residuals for three “classic” mil-lisecond pulsars. Excellent agreement is found between the post-upgradepulse arrival times, and the expectations from pre-upgrade ephemerides.(Courtesy of Alex Wolszczan).


[email protected] look at:http://astro.berkeley.edu/~mpulsar.

The Caltech pulsar group has success-fully installed, and started regular tim-ing observations with, the CaltechBaseband Recorder (CBR). This in-strument is capable of sustained dual-polarization 10-MHz, 2-bit, basebandobservations. Based on a fast flexibledigitizer board, observations at twicethis bandwidth or with 4-bits are pos-sible for up to 20 minutes until the diskstorage fills up. The recording systemis based on a SUN workstation with aset of disk drives to buffer the data priorto writing to 2 DLT-7000 tape drives.The data acquisition software has beenwritten to accommodate variable num-bers of disks and tape drives to allowincreased bandwidth observations asfaster recording technology becomesavailable. In addition, the acquisitionsoftware de-stripes the data as it istransferred from disk to tape to allowfor off-line analysis of the data on sys-tems which have only a single tapedrive. Based on the same data acqui-sition and monitoring software as thePSPM, the operation of the CBR al-lows for real-time diagnostics and re-mote monitoring.

thogonal polarization channels, allow-ing 10-MHz bandwidth with 2-bit sam-pling or 5-MHz bandwidth with 4-bitsampling, and producing a continuousthroughput of 10 MB/s. The resultingdata stream passes through a SPARC-20 computer, on to DLT-7000 tapedrives and/or a 108-GB disk array.Data analysis is performed off-line bya fast (1.25-Gflop) parallel processor.The effects of dispersion are removedby filtering the data time-series withthe inverse of the interstellar medium“chirp function”. Cross-products areformed from the dedispersed signals,and then can be folded modulo thepulse period. In this fashion, fullStokes parameters are obtained for ev-ery observation. Narrow-band radio-frequency interference can be excisedas part of the coherent signal-process-

The Caltech pulsar group, in collaborationwith the group at Berkeley, has also in-stalled the first 50% of a wide-bandwidthdigital filter-bank — the Berkeley AreciboCaltech Swift Pulsar Instrument(BACSPIN). Based on the same hardwareas a similar instrument running at Nancay(the NBPP), this instrument will be capableof ~200-MHz bandwidth observationswhen installation is completed in the springof 1998. Both BACSPIN and the CBR arehosted by the same Sun computer and arecapable of acquiring data simultaneously.It is planned to tightly couple these two in-struments in the future. For example, itshould be possible to use the real-timebroadband capabilities of BACSPIN tosteer the CBR to record only the brightscintillation peaks of a given pulsar. Forplots of the “first noise” observations withthe CBR and BACSPIN, see:http://www.srl.caltech.edu/personnel/sba/instruments/pulsar.

Late last year, Ingrid Stairs (Princeton) re-installed the Princeton Mk-IV pulsarbackend at Arecibo, following themachine’s extended stay at Jodrell Bank.The Mk-IV is designed to increase pulsartiming precision by implementing the tech-nique of coherent dedispersion in softwareover large bandwidths. A fast analog-to-digital converter samples quadrature com-ponents of the received voltages in two or-

Fig. 6: Full-polarization pulse profiles for PSRB1937+21 at 1420 MHz (top), and PSRJ0621+1002 at 430 MHz (bottom). The upperpanels show total intensity (heavy solid line),linear polarization percentage (dotted line),and circular polarization percentage (light solidline), while polarization position angles areshown in the lower panels. The data weretaken with the Princeton Mk-IV backend.(Courtesy Ingrid Stairs).

Fig. 5: An L-band integration on PSR J1713+0747 using the Arecibo-Berkeley Pulsar Processor(ABPP). (Courtesy Don Backer).


ing task, while time segments contami-nated by broad-band noise are deleted.Preliminary results from the Mk-IV in-clude L-band observations of the fast-est millisecond pulsar, PSR B1937+21,yielding timing uncertainties of lessthan one-fifth of a microsecond, (a full-polarization pulse profile from these1420-MHz observations is shown inFig. 6 top) and observations of PSRJ0621+1002, a neutron star-whitedwarf binary pulsar discovered by thePrinceton group during their upgradesurvey (a 430-MHz profile is shownin Fig. 6 bottom). Princeton timingwork will initially be centered on“shaking down” the new instrumenta-tion and connecting new observationsto pulse-timing models developed be-fore the upgrade.

A unique development was pioneeredrecently by Xilouris and Bill Sisk(NAIC). It is now possible for the dif-ferent pulsar research groups to tap offof the same I.F. during observations,using as many as five independentbackends to collect data simulta-neously. This provides remarkable po-tential for collaboration between ob-servers. In early 1998, a consortium ofobservers from Berkeley, Caltech,Jodrell Bank, MIT, NRL, Penn State,and Princeton began regular timing ob-servation of standard millisecond pul-sars. To date (March 29th), six sessions,spaced roughly weekly, have been ob-served, the data being taken byXilouris. This has covered some half adozen targets, using 4 or 5 separatepulsar backends. The initial resultsindicate that the timing residualsachieved at L-band by the variousbackends are unprecedentedly small,the many innovations in data-takinghardware providing significant im-provements over the system availablepre-upgrade. This, plus the excellentsignal-to-noise already achieved at L-band, allows timing residuals below100 nanoseconds, an accuracy thatopens new scientific horizons to pul-sar timing. Such observations providean extremely powerful tool whensearching for pulsar companions with

masses as low as asteroids, can probe thedifferential acceleration caused by the Ga-lactic disk, yield sensitive measures of thestructure of the interstellar gas, and ap-proach the precision needed to study long-period gravitational waves.

In addition, coordinated timing measure-ments using the different pulsar backendsthat share the Arecibo I.F. help determinethe role that instrumentation plays in de-limiting the timing precision at the sub-microsecond level. Further, it is now pos-sible to switch between 430 and 1420 MHzin about 30 seconds, which can be used toyield sensitive measures of the structure ofthe interstellar gas, and also permit the re-moval of interstellar effects from timing.

The Arecibo Observatory Fourier Trans-form Machine — (AOFTM) — AnNAIC Facility Pulsar Backend.Zaven Arzoumanian, Maura McLaughlin,Jim M. Cordes (Cornell)

The Arecibo Observatory Fourier Transform Machine (AOFTM) is a new

NAIC facility instrument, ideally suited forpulsar-search and single-pulse studies.Shake-down and testing of the 10-MHz,1024-channel, Fourier transform spectrom-eter is nearly complete, as is the web-baseddocumentation for the hardware and data-

acquisition control software. Quick-look and data-handling software arealso provided. The spectrometer andsampling system allow useful trade-offs between channelization and timeresolution — the default configurationis for 1024 channels and 102.4 µs sam-pling (2 bits), yielding a maximum datarate of 2.5 MB/sec. The shortest avail-able sample interval, for 16 channelsacross 10 MHz, is 16 microsec. Dataoutput options include a 9-GB disk (ca-pacity limited to 50 minutes of obser-vations at the full data rate), standard8mm “Exabyte” tape (limited to maxi-mum data rates of 0.5 MB/sec), or8mm Exabyte “Mammoth” tape, thestorage medium of choice for full-data-rate applications with the AOFTM.The AOFTM’s features will signifi-cantly improve search sensitivity tofast, highly-dispersed pulsars over thatattainable with existing data-acquisi-tion systems at Arecibo. For a descrip-tion of the expected gains in sensitiv-ity, visit:h t t p : / / w w w. n a i c . e d u / ~ a o f t m /sensitivity.html.For single-pulse studies, the AOFTMprovides good dynamic range through8-bit sampling in 256 channels over 2.5MHz.

Fig 7: The dynamic spectrum of PSR B0834+06 at 47 MHz made with the AOFTM. The foldedpulsar profile is analyzed into 165 frequency channels. The observing parameters were: dt=0.1024ms, p=1273.67259 ms, total time=599 s, bw=1.830859 MHz.

Fre

quen

cy C

hann

el


During test observations through De-cember 1997, nine known pulsars weresuccessfully observed at three frequen-cies (47, 430 and 1420 MHz). For anexample of a dynamic spectrum of pul-sar PSR B0834+06 made at the very-low frequency of 47 MHz via theAOFTM (see Fig. 7). A set of sum-mary pulse profiles can be viewed at:

h t t p : / / w w w. n a i c . e d u / ~ a o f t m /detections.html.In addition to the pulsars displayedthere, the pulsars B0301+19,B0823+26, and B0919+06 were de-tected at 430 MHz; these objects aresufficiently bright that observationsmade with 2-bit sampling in 10-kHzchannels suffer from saturation. Re-maining work includes testing the tim-ing properties of integrations triggeredby the Observatory 10-sec tick and im-proving real-time diagnostic output.

Receiver Status and PlansPaul Goldsmith

The past few months have been asomewhat difficult time as we

struggle to get receivers installed andcalibrated. A great deal of work hasgone on which should bear fruit in thenear future.

The Gregorian and CH 430 MHz sys-tems have been working quite steadily,and used extensively for pulsar timingand atmospheric radar work.

The 610 MHz system has beenequipped with fairly narrow band fil-ters defining the protected frequencyband of only 6 MHz width, and exclud-ing nearby harmful TV stations. Thecalibration system has also been as-sembled, and the whole system shouldbe reinstalled before the end of March.

The L-narrow (1.3 - 1.45 GHz) systemhas been on the telescope, and used forpulsar observations. The L-wide sys-tem (1.15 - 1.75 GHz) is having a num-ber of minor problems worked on.Both the system noise calibration andrelative phase adjustment of the two

channels will be carefully completed be-fore it is reinstalled in the Gregorian. Wehave had a second L-band feedhorn built,which has just arrived in Arecibo. This willallow installation of BOTH L-band sys-tems, and comparisons for use with RFIexcision and other possible applicationscan be made. It is possible that we canoperate both systems simultaneously, al-though the exact routing through the IF/LO system needs to be checked out. Inany event, we do anticipate that we will bein a good position to support L-band op-erations both for on-going pulsar work andfor spectroscopy.

A new S-band radar receiver has been as-sembled. It uses a turnstile junction, so itsbandwidth is limited to about 100 MHz. Itincorporates HEMT amplifiers, and al-though there is a stability problem with onechannel, it is expected that this will have astraightforward cure. This system is ex-pected to replace the maser amplifier pre-viously used in this application.

The broadband S-band system is beingcompleted in Ithaca. Circulators have beenreceived that should ensure stable perfor-mance. A feedhorn has been fabricated.The newest member of our engineeringstaff, Donna Kubik, is working for the timebeing in Ithaca. She will work with GeneLauria to complete the assembly and testof this system.

The 4-6 GHz C-band system has been re-installed in the Gregorian. We expect touse it to make system tests in the monthsahead.

A detailed analysis of the “suckout” in the8-10 GHz receiver has been completed byGene Lauria, and remedied by someremachining. When time and weather inIthaca permit, this system will be retested.

Other EffortsProfessor Jim Breakall from Penn StateUniversity is spending a sabbatical semes-ter at Arecibo. He is working on differentbroadband feed designs for relatively lowfrequency systems (below 1.5 GHz) for theGregorian. These may be useful for a sys-tem in the 327 MHz band and possibly formulti-frequency pulsar receiver systemsdown the road.

Innovative Filter Design Protects L-band ObservationsRobert Zimmermann & Tapasi Ghosh

Radio astronomy observations arebecoming increasingly difficult in

a world of global communication.While the telescope itself must be sen-sitive to incredibly weak signals fromother galaxies, it must also be able towithstand simultaneous strong earthbased signals, often on adjacent sig-nal channels! Such is the case forArecibo L-band observations.

The new wide-band L-band receiver(L-wide) can cover a frequency rangeof about 1.0-1.9 GHz, albeit with slightdegradation of the system performancetowards the band edges. However,there are many other active spectrum-users in this range whose radiation fieldat the Observatory can cause gain-com-pression in the RF post-amplifiers ofthis receiver. From our round-the-clock, hill-top spectrum monitoring,and also from data gathered through thereceiver in the Gregorian dome, it wasindeed confirmed to be so. The elec-

1120 MHz

1220 MHzRADAR

BAN

AEROSTAT Radar1246, 1261 MHz

1241, 1256 MHz

1370 MHz

1274.5 MHz1294.6 MHz1306.9 MHz

1621 - 1627 MHzIRIDIUM Downlink

1750 MHz

Cellular Phones etc.

"D

L-band EM Environment at AO

1330, 1350 MHzFAA Radar

(Schematic diagram)

"


tromagnetic environment at the Obser-vatory within this range of frequen-cies can be schematically representedas shown in the L-band Environmentfigure, where ONLY the very strong ra-dar/radio transmitters are marked.

In order to be able to use most of thiswide frequency range, an innovativecomputer-controlled filter-bank sys-tem, plus a programable radar blankerare currently under construction.

A schematic diagram of the filter-bankcircuitry is shown above. The radarblanker will be described in a futureissue.

The filter bank will be located imme-diately following the cooled RF am-plifiers and before the post RF ampli-fiers. The present status of various fil-ters consituting the filter-bank is :

Catagory A

1. HPF1: 1370 MHz and above (waveguide filter); in place.

2. HPF2: 1640 MHz and above (waveguide); under construction.

3. HPF3: 1320 MHz and above (waveguide); available soon (this optionmay have to be used in conjuctionwith the radar blanker, blanking thetwo FAA radars at 1330 and 1350MHz).

4. BPF1: 1150-1750 MHz; in place.

5. BPF2: 1120-1220 MHz; ordered.

Catagory B - Filters covering 1220 - 1320MHz (radar) band: For these, the possibili-ties are:

1. A number of Band-pass filters of 25MHz bandwidth, covering the aboverange, along with the radar blanker,called into action for blanking theapproriate radars within the pass-band.

2. A bandpass filter similar to BPF2, butcovering 1120-1265 MHz. This way,1220-1265 MHz will be useable inconjuction with the blanker being usedfor just the two aerostat radars. How-ever, this will also mean that 1265-1320MHz will be very difficult to use, whereone would need to employ the full po-tential of the newly designed blankerand might lose a lot of time to blank-ing.

Catagory C - Special filter:

1. Superconducting band-reject filterto remove IRIDIUM down-link, be-tween 1621.35-1626.5 MHz:The prototype filter, already testedat Superconductor Technologies,provides 55 dB suppression overthis range, with much less than 1dB loss in the radio astronomyband. It operates in a 70 K dewar.

We hope that this gives the users anopportunity to gather reasonably cleanL-band data where software techniquescan thereafter be applied to extract thecosmic signal.

The New Ionosonde AntennaRobert Zimmermann

The Observatory’s digitalionosonde has a new log-periodic

antenna. Supported from a 30 metertower, it provides a vertical gain ofabout 6 dB, allowing “textbook style”ionograms to be made under virtuallyany atmospheric conditions (see Fig.8). The data is routinely used by theionospheric group to support 430 MHzincoherent scatter radar observations.Also, the ionospheric information isused by radio astronomers to determinethe anticipated “Faraday rotation” oflinearly polarized signals within theionosphere.

The antenna is actually a dual orthogo-nal log-periodic dipole array, designedand built by Penn State graduate stu-dent Nathan Miller under the guidanceof Professor Jim Breakall. Theionosonde uses one of the antennas asa transmitting antenna, with the sec-ond to receive the signal reflected fromthe ionosphere (functioning like asmall bistatic radar station).

The new facility saw its “first use” dur-ing the COQUI-II sounding rocketcampaign. The rocket launching crite-ria were specified in terms of particu-lar ionospheric conditions, in the di-agnosis of which the ionosonde playedan important role.

2 3 4 5 6 7 8 9 10 11

100

150

200

250

300

350

400

450

500

AOS Feb 26 12:01:22 1998

Frequency (MHz)

Virtu

al H

eig

ht

(km

)

Fig. 8: A typical ionogram from our new sounder.

Schematic diagram of L-Band filter bank.


AO Computing NewsArun Venkatraman

Observers in the re-arranged Control Room will use a Sun

UltraSPARC 170 workstation with 20"monitor, connected to the data acqui-sition ethernet and to the observatoryfileserver over a new Fast ethernetlink. A second workstation is availablenearby for a co-observer. TheUltraSPARC has over 20 GB disk fortemporary data storage during experi-ments. Data will be periodically movedto the fileserver over the fast ethernet,and can also be backed up to a local8mm tape drive.

Realtime displays in the Control Roominclude :

1. telescope pointing, status and otherrelevant information,

2. drive system and receiver statusand,

3. real-time telescope data.

The User Interface for radio astronomyis based on the ADAM (Arecibo DataAcquisition and Monitoring) languagespecification. Although originallyspecified as a command-line system,the language now supports a graphicalinterface which simplifies commontasks via point-and-click widgets (thecommand-line interface is also avail-able). Observers may use their owncatalogs of sources formatted as de-scribed in the ADAM manual. The Ob-servatory currently provides a standardsource catalog, a standard line fre-quency catalog and a pulsar catalog.The experiment setup facility includesfront-end (receiver selection, IF systemconfiguration, selection of noisesources for calibration, Doppler correc-tion), back-end (Continuum, SpectralLine, Pulsar, VLBI), procedures (po-sition or frequency switching, map-ping, simple on-offs, pointing checks,etc.), and utilities (catalog browser, fileimport). Observing files may be cre-ated in the ADAM language off-line,using either the graphical interface or

a text editor. The run-time facility permitsobserving files to be queued while beingedited.

A standard scheme to support visitor-sup-plied back-ends, including telescope sta-tus reporting and time synchronizationtools, is under development.

Most observatory data will be taken on 8-mm tape media, although a 4-mm drive isavailable off-line to make copies. The 8-mm drive lineup includes Exabyte Mam-moth (20 GB capacity) for data-intensiveexperiments. As in the past, tape cartridgesassigned to observing projects are givenAO numbers and remain at the Observa-tory, although visitors may copy the datato take with them. The Observatory’sANALYZ program (aged 20-somethingand still vigorous) is currently used formonitoring and displaying incoming tele-scope data. Limited support via a commonfile format is planned for other packages,including CLASS, Single Dish AIPS(++)and IRAF. The commercial packages IDL(from Research Systems Inc.) andMATLAB (from The Math Works Inc.) arealready supported on the Observatory net-work, although no analysis software sub-system at the AO is based on them.

With the recent acquisition of 15 SunUltraSPARC systems including an Ultra30, the AO is equipped to handle comput-ing tasks requiring 5-10 times more CPUspeed and storage capability than providedby the previous generation of desktops. Welook forward to new results from more so-phisticated fitting techniques, longer FFTsand faster searches!

Coordination Agreement betweenNAIC and Motorola-IRIDIUMTapasi Ghosh

The National Astronomy and Ionosphere Center, which operates the

Arecibo Radio Telescope, and MotorolaInc., which operates the IRIDIUM satel-lite system, have signed a CoordinationAgreement between the IRIDIUM systemand the Arecibo Observatory. The Agree-ment addresses potential interference pro-duced by the communication satellite sys-

tem with observations of the astro-nomically important 1612 MHz line ofthe OH molecule in the 1610.6 - 1613.8MHz band. The Agreement guaranteesthat :

(a) during scheduled observations inthis band, between 10 pm and 6 amMiami local time, IRIDIUM’s out-of-band emission will be below the-238 dBW/m2/Hz. level for allseven days of the week,

(b)during day time, up to 8 passes peryear will be available for observa-tions defined as targets of opportu-nity that could not be observed us-ing a blanker provided by IRI-DIUM. Such objects includes com-ets, supernovae and other celestialobjects that are of unknown natureas yet.

We congratulate Drs. Willem Baan,Mike Davis, Paul Goldsmith, ThomasGergely (of NSF) and Atty. PaulFeldman (Fletcher, Heald & Hildreth,P.L.C.), for this successful outcome oftheir persistent efforts in this negotia-tion process spread over several years.The major achievement for the as-tronomy community has been the in-clusion of the level below which IRI-DIUM has agreed to restrain their out-of-band emission. However, in orderto perform observations outside the 8hours at night, NAIC will have to in-stall very expensive superconductingband-reject filter so that the effect ofthe downlink can be suppressed to atolerable level at all times.

Nevertheless, Radio astronomers atNAIC are pleased that, after manyyears of effort, the ability to carry outthis type of observation fully exploit-ing the unique sensitivity of the newly-upgraded Arecibo telescope will beguaranteed. At the final stage, the ne-gotiations were facilitated by represen-tatives of the Federal CommunicationsCommunication (FCC), the NationalTelecommunications and InformationAdministration (NTIA). NAIC isthankful to them.


The discussions during the long nego-tiating process have resulted in an in-creased awareness on the part of bothradio astronomers and communicationsengineers of the need to coordinatespectrum usage very carefully. In par-ticular, the placement in frequency ofthe satellite down link bands needs tobe carefully evaluated.

Arecibo Observatory/Angel RamosFoundation Visitor Center celebrates oneyearDaniel R. Altschuler and José L. Alonso

Although it seems as if it were inaugurated yesterday, we recently cel-

ebrated the first year of operations of theArecibo Observatory/Angel Ramos Foun-dation Visitor Center. It has been by allmeasures a very successful year surpass-ing by far our expectations. The number ofyearly visitors has more than tripled, reach-ing over 125,000 for this first year, about

one third of these being school chil-dren. Of greater importance is the factthat feedback from visitors indicatesgreat satisfaction with their experi-ences. Many have written letters ex-pressing their appreciation for the Ob-servatory in respect to the educationalwork we are engaged in.

Improvements have already beenmade, including a new pedestrian ac-cess road with two shelters, a picnicarea, a CCTV security system and avery popular hotdog cart. A new ve-hicle has also been purchased for thecenter.

With the new facility and its related hu-man resources, we are now able toschedule 10-12 school groups perweek, almost three times what waspreviously possible. More importantis the fact that the visiting public,teachers, and students in particular areexposed to an active learning experi-ence, making AOVEF a valuableteaching resource. Over 500 schoolsfrom all over Puerto Rico visited dur-ing this first year.

A collaborative program between theArecibo Observatory and the AreciboCampus of the University of PuertoRico allows science majors from thecampus to be selected as Visitor Cen-ter tour guides. A group of 13 studentswere selected to work during this firstyear and we are currently interview-ing a group of twenty new students.Participants receive on-site trainingabout observatory operations, includ-ing technical aspects of the telescopeand its related science.

During the summer, a teacher in resi-dence developed a “School VisitGuide” which includes a set of keyquestions related to every exhibit, andthe connections between the subjectmatter presented and the actual schoolcurriculum. This guide helps teachersorganize their school group visit to theObservatory more effectively.

The Visitor Center became a focalpoint during the February 26 partial so-lar eclipse and was visited by a large

Cover page of “El Nuevo Día” for February 27, 1998. It featured a photo of the activities at the VisitorCenter titled, “Curiosity shines”. We have inserted another photo which appeared in the San JuanStar of the same day.


number of groups which participatedin eclipse tours. During the eclipse, itwas the source of live images transmit-ted by a local TV station. Over theyear, the visitor center auditorium hasbeen used for teacher workshops, pressconferences, special lectures for visit-ing groups, and scientific symposia. Inearly April of 1998 we hosted a oneday session (out of seven) of the“Tropical Workshop on Particle Phys-ics and Cosmology” organized by theUniversity of Puerto Rico, Rio Piedras.About 100 participants from outsidePuerto Rico attended this meetingwhich featured lectures by over twentyspeakers including Nobel Prize laure-ates Joseph Taylor and SheldonGlashow.

We are pleased with our first year ofoperations and look forward to anequally fruitful second year.

(The May issue of Sky & Telescopewill feature a nice article on our Visi-tor Center. - The Editors)

Comings and Goings

Hasta Luego, WillemChris Salter

After spending 15 years at AreciboWillem Baan is leaving our group

of staff scientists. Willem, a Senior Re-search Associate with NAIC, departedfor Dwingeloo in the Netherlands at theend of January. There he takes up theposition of Director of the WesterborkSynthesis Radio Telescope (WSRT).Great responsibilities await him in this

job asDwingeloomoves intoa period ofreorganiza-tion, andthe WSRTe m e r g e sfrom itsown up-grade.

Originally, Willem came to astronomy bya somewhat indirect route, having a degreein Engineering from the University ofDelft. He then moved to the USA, and intoastronomy, receiving both his M.Sc. andPh.D. degrees from MIT. Following spellswith the Institute for Advanced Study,Princeton, and Penn State, he joined theRadio Astronomy staff at Arecibo in Sep-tember 1983. Whilst at Penn State, Willemhad already used the 305-m telescope todetect the first OH “megamaser”, in theform of broad-line OH emission from thestarburst galaxy, Arp 220. Today, over 50OH megamaser, and even gigamaser, gal-axies are known, many discovered byWillem and his collaborators. These in-clude the most distant example, IRAS14070+0525 at z = 0.265, discovered atArecibo in 1991. He was also responsiblefor showing that within the standard modelof OH megamasers, with low-gain ampli-fication occurring in a molecular discaround the galactic nucleus, the gas ispumped by far-infrared radiation and am-plifies the nuclear continuum emission.Willem also established an additionalmember of the “maser zoo” when he iden-tified the first extragalactic formaldehydemasers in NGC253 and Arp 220, later add-ing further examples through his Areciboobservations with the mini-Gregorian.Apart from his main field of maser emis-sion from galaxies, Willem has shown hiswider breadth of interest via his many otherinvestigations of dense molecular gas in ga-lactic nuclei, this aspect being exemplifiedby his excellent review of the subject (withChristian Henkel and ReinerMauersberger); a 1991 publication in“A&A Review”. He is also active in thestudy of galactic masers.

The name “Willem Baan” is also synony-mous with the radio-astronomers’ fightagainst the inroads of radio frequency in-terference (RFI). He is presently the Chair-man of IUCAF, the Inter-Union Commis-sion on Frequency Allocations for RadioAstronomy and Space Science, and there-fore an ex-officio member of CORF (theU.S. Committee on Radio Frequencies). Healso serves as a member of the WorkingGroup 7D of the Radio CommunicationSector of the ITU, takes an active part in

both ITU-R Study Groups 1 (spectrummanagement) and 7 (science services),and protects radio astronomy’s inter-ests at ITU-R WorldRadiocommunication Conferences(WRCs).

On a more local level, Willem has beeninvolved in RFI work at Arecibo formany years. Apart from an array of in-dividual successes during this time, healso took a major hand in establishingthe Puerto Rico Spectrum Users Group(PRSUG). In Arecibo, his name willalways be inseparable from the estab-lishment of the recently implementedPuerto Rican Coordination Zone(PRCZ), through which a new licenseseeker intending to operate on the is-land below 15 GHz is required topresent a copy of the technical detailsof his application to NAIC, who thenhave 20 days to consider the potentialof such a system for interfering withobservatory operations and to work outa mutually acceptable solution. (Incases of dispute, the FCC reserves theright to either withhold or grant the rel-evant licenses.) The setting up thePRCZ will certainly be of great long-term benefit to both the Observatoryand its users; yet another guarantee thatWillem will not be forgotten here.

Willem is leaving us for a position ofhigh responsibility, and we wish himall the very best with the many chal-lenges this represents. Nevertheless, weknow that the fine match between theupgraded Arecibo telescope’s perfor-mance and the demands of Willem’spersonal research will not go unheeded,and we expect to see him back hereagain and again. He certainly will becoming back in the near future, havingdeclared his intention of helping withthe re-commissioning of the 305-mtelescope. In fact, as we wave Willem,Lydia and their three children goodbye,and wish them all happiness and suc-cess for the years ahead, we know thatwe are not really saying “Adios”, butonly “Hasta luego!”


Visitors and N ew People

Joel Weisberg (Carleton College)Early this year, Arecibo had the greatgood fortune of a two-month sabbati-cal-leave visit from our old friend, JoelWeisberg, noted pulsar astronomer andProfessor of Physics and Astronomy atCarleton College, Minnesota. Over theyears, Joel has been one of our mostregular (and popular) telescope users.His recent visit provided stimulus toall of us on the radio astronomy staff,and his sunny presence raised a smilewith everyone in the Observatory.While here, Joel contributed consider-ably towards our preparations for a po-larimetry capability with the upgradedtelescope. It is only sad that his visitwas not to include any observing thistime around, although we are sure thatthis will be rectified in the near future.Joel, it was great having yourself, Janet,and little Ben down here in January andFebruary. Come back soon — all threeof you!

Jim Breakall (Penn State University)is spending a 4-month sabbaticaland will be atArecibo until May1. He is workingon the ionosondeantenna alongwith his graduate

student, Nathan Miller (Penn State).In addition, he is working on low-fre-quency broadband antennas for theGregorian system.

Ludmila Kagan (Radiophysical Re-search Institute,N i z h n yNovgorod, Rus-sia) - is workingwith Prof. MichaelKelley (Cornell)providing theo-retical support onunders tand ing

ionospheric structures and disturbancesusing data from the Cornell all-sky im-ager. She holds a four month term as avisiting scientist.

Brent Grime (Penn State University) par-ticipated in the November 1997 Leonids ex-periment and then returned for the Febru-ary-April 1998 Coqui-II campaign. Brentwas a 1997 REU Summer Student atArecibo as well. The lidar/radar data he iscollecting and analyzing during these stud-ies will be part of his Master’s thesis workat Pennsylvania State University, where heworks in Tim Kane’s lidar group. He alsorecently received his Air Force Commis-sion.

New Operations TechnicianPedro Torres, our new Operations Tech-nician has a Bachelors degree in PhysicsApplied to Electronics from the Universityof Puerto Rico, Humacao Campus. He hasworked as a Communications Technician,Music Instructor, Observatory Technician,Electronics Technician, and has done re-search in Pentium and Pentium Pro Archi-tecture.

He is currently attending the PolytechnicUniversity of Puerto Rico for a Masters inManagement Engineering. He is a Cuatroplayer with the Rondalla de Humacao, P.R.He is also a volunteer in the Oficina deAsuntos de la Juventud in the Grupo AsesorFederal de Programa de Justicia Juvenil yPrevención de la Delicuencia at the Oficinadel Gobernador. Pedro is an excellent ac-quisition to the Operations Department andthe Observatory.

Jochen Meier is a student of electronicsvisiting us from Fachhochschule Augsburg,Germany. He will be here 20 weeks in all,from March 1 through July 19 to work onthe design and construction of a radarblanking system for the receivers.

Rafael Mojica is a student in the com-puter science department at the Uni-versity of Puerto Rico, Arecibo Cam-pus. He is doing a 200 hour internshipdeveloping a maintenance database foruse in the electronics department.

José Francisco Salgado, “Paquito”has been coming to the Arecibo Ob-servatory since his undergraduate daysat UPR Río Piedras as a summer stu-dent with Daniel Altschuler. Sincethen he has moved on to the graduateprogram in astronomy at the Univer-sity of Michigan. Currently he is work-

ing on his thesis project, characteriz-ing the distribution of ionized interstel-lar medium via observations of scat-ter-broadening of extragalactic sourceswith Chris Salter and Tapasi Ghosh.Paquito has now moved to the Obser-vatory on a long-term basis. He is “un-der orders” to finish his thesis quickly.In his spare time he has taken on theresponsibility of co-editor for theNewsletter. He is also a Mac “guru”,and the new look of our Newsletter ishis creation.

New AssignmentAngel “Guelo” Vazquez, long knownin local circles as PC-Doc, has joinedthe Computer Department as Program-mer. Angel is primarily responsible forconfiguration and upkeep of the 50+and growing PC network at the Obser-vatory. In addition to his knowledgeof the ins and outs of Microsoft Win-dows and various PC-based softwarepackages, Angel brings his broader“networking” skills as a ham operatorand Web page designer.

Jim Breakall

Mila Kagan

Pedro Torres

TO:

NAIC/Arecibo Observatory Newsletter504 Space Science BuildingCornell UniversityIthaca, NY 14853-6801 U.S.A.

*address correction requested

NAIC/AO Newsletter is published three times per year by theNational Astronomy and Ionosphere Center.The NAIC is operated by Cornell University under a cooperativeagreement with the National Science Foundation.

Tapasi Ghosh, Jonathan Friedman & José F. Salgado, Editors

Address: NAIC/AO NewsletterP.O. Box 995Arecibo, PR 00613-0995

Phone: +1-787-878-2612Fax: +1-787-878-1861E-mail: [email protected] or [email protected]: www.naic.edu

march - arecibo observatory

Documents