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Space News Update — May 5, 2015 —

Contents

In the News

Story 1:

Rock Spire in 'Spirit of St. Louis Crater' on Mars

Story 2:

The Deep Space Atomic Clock

Story 3:

NASA's NuSTAR Captures Possible 'Screams' from Zombie Stars

Departments

The Night Sky

ISS Sighting Opportunities

NASA-TV Highlights

Space Calendar

Food for Thought

Space Image of the Week

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1. Rock Spire in 'Spirit of St. Louis Crater' on Mars

Rock Spire in 'Spirit of St. Louis Crater' on Mars (False Color). An elongated crater called "Spirit of St. Louis," with a rock

spire in it, dominates a recent scene from the panoramic camera (Pancam) on NASA's Mars Exploration Rover

Opportunity. Image Credit: NASA/JPL-Caltech/Cornell Univ. /Arizona State Univ.

An elongated crater called "Spirit of St. Louis," with a rock spire in it, dominates a recent scene from the

panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity.

Opportunity completed its 4,000th Martian day, or sol, of work on Mars on April 26, 2015. The rover has been

exploring Mars since early 2004.

This scene from late March 2015 shows a shallow crater called Spirit of St. Louis, about 110 feet (34 meters)

long and about 80 feet (24 meters) wide, with a floor slightly darker than surrounding terrain. The rocky

feature toward the far end of the crater is about 7 to 10 feet (2 to 3 meters) tall, rising higher than the crater's

rim.

The component images of this mosaic view were taken on March 29 and 30, 2015, during Sol 3973 and Sol

3974 of the mission. This version of the image is presented in approximate true color by combing exposures

taken through three of the Pancam's color filters, centered on wavelengths of 753 nanometers (near-infrared),

535 nanometers (green) and 432 nanometers (violet).

The unusually shaped Spirit of St. Louis Crater lies on the outer portion of the western rim of Endeavour

Crater. Endeavour spans about 14 miles (22 kilometers) in diameter, and Opportunity has been exploring its

western rim for about one-third of the rover's mission, which has lasted more than 11 years. Endeavour's

elevated western rim extends northward to the left from Spirit of St. Louis Crater in this scene. A glimpse of

the far side of Endeavour is visible on either side of the rock spire.

Source: NASA Return to Contents

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2. The Deep Space Atomic Clock

Sharing a ride on the Orbital Test Bed satellite owned by Surrey US as part of a U.S. Air Force mission, the Deep Space

Atomic Clock will undergo a year-long shakeout in space. Credits: NASA/JPL

As the saying goes, timing is everything. More so in 21st-century space exploration where navigating

spacecraft precisely to far-flung destinations—say to Mars or even more distant Europa, a moon of Jupiter—is

critical.

NASA is making great strides to develop the Deep Space Atomic Clock, or DSAC for short.

DSAC is being readied to fly and validate a miniaturized, ultra-precise mercury-ion atomic clock that is orders

of magnitude more stable than today’s best navigational clocks.

Slated for a boost into space in 2016, DSAC will perform a yearlong demonstration aimed at advancing the

technology to a new level of maturity for potential adoption by a host of other missions.

Stability in space

The upcoming DSAC mission will deliver the next generation of deep-space radio science. At first blush, that

may seem humdrum. But here’s the wake-up call stemming from such work on a timepiece for tomorrow…

For one, the Deep Space Atomic Clock will be far more “stable” than any other atomic clock flown in space, as

well as smaller and lighter. Stability is the extent to which each tick of the clock matches the duration of every

other tick.

At its core, DSAC is a “paradigm shifting” technology demonstration mission to exhibit how to navigate

spacecraft better, collect more data with better precision and boost the ability for a spacecraft to brake itself

more accurately into an orbit or land upon other worlds.

The DSAC project is sponsored by NASA’s Space Technology Mission Directorate and managed by NASA’s Jet

Propulsion Laboratory (JPL) in Pasadena, California.

Flight-ready demonstration unit

At JPL, the DSAC flight-ready demonstration unit is assembled. Further environmental testing, performance

optimization and other activities are being completed.

In the laboratory setting, DSAC has been refined to permit “drift” of no more than 1 nanosecond throughout

10 days. Drift is when a clock does not run at the exact right speed compared to another clock.

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“Transitioning the technology from the lab, where environments are very stable, to the launch and space

environments—where they are much more variable—has presented some unique challenges to DSAC’s design,” says

Todd Ely, principal technologist for the DSAC Technology Demonstration Mission.

For example, Ely points to temperatures in orbit that vary daily and seasonally. They can affect clock function if not

carefully considered. Then there are gravitational loads placed on the instrument during launch that can reach up to

14g (14 times the gravity of Earth). Those g-stresses can strain the clock’s structure and must also be accounted for

in DSAC’s design.

“These are just a couple of factors that have led to DSAC’s robustness,” Ely says.

In-orbit test

The DSAC demonstration unit and payload are to be hosted on a spacecraft provided by Surrey Satellite

Technologies U.S. of Englewood, Colorado, and lofted spaceward as part of the U.S. Air Force's Space Test Program

(STP)-2 mission aboard a Space X Falcon 9 Heavy booster.

The DSAC payload will be operated for at least a year to demonstrate its functionality and utility for one-way-based

navigation. The clock will make use of GPS satellite signals to demonstrate precision orbit determination and

confirm its performance.

Once DSAC is in orbit, what are the steps to successful testing? “Our in-orbit investigation has several phases

beginning with commissioning, where we start up the clock and bring it to its normal operating state,” Ely responds.

“After that we’ll spend the first few months confirming and updating our modeling assumptions, which we will use

to validate the clock’s space-based performance,” Ely adds. “With these updates and our observation data, we’ll

spend the next few months determining DSAC’s performance over many time scales…from seconds to days.”

Infusion for the future

Ely says that from that point, the DSAC team transitions to a less intense mode, one in which they will monitor clock

telemetry. By using that data, ground controllers can characterize the atomic clock’s potential for long life

operations.

“This will be important data for the next generation DSAC, where its lifetime for deep space would most likely need

to be many years,” Ely says. The DSAC flight in 2016 will identify pathways to ‘spin’ the design of a future

operational unit to be smaller and more power efficient, he adds.

Indeed, DSAC is an ideal technology for infusion into deep space exploration. One future use of DSAC follow-on

application includes Mars-bound spacecraft that need to aerobrake accurately into the red planet’s atmosphere.

Transformational technology

Yet another DSAC-inspired duty is to help confirm the existence and characteristics of a possible subsurface liquid

ocean on Europa. Any liquid/ice ocean on the enigmatic moon would be affected by nearby giant Jupiter. DSAC

technology could make possible global estimations of the subsurface ocean.

Estimation of Europa’s gravitational tide, Ely says, provides an example of the use of DSAC-enabled tracking data

for Europa gravity science.

DSAC-enabled high-quality one-way signals for deep space navigation and radio science can enhance radio science

at Europa, Mars and other celestial bodies, Ely concludes. DSAC has the potential to transform the traditional two-

way paradigm of deep space radiometric tracking, he says, to a more flexible, efficient and extensible one-way

tracking architecture.

Source: NASA Return to Contents

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3. NASA's NuSTAR Captures Possible 'Screams' from Zombie Stars

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has captured a new high-energy X-ray view (magenta) of the

bustling center of our Milky Way galaxy. The smaller circle shows the center of our galaxy where the NuSTAR image was

taken. Credits: NASA/JPL-Caltech

Peering into the heart of the Milky Way galaxy, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) has

spotted a mysterious glow of high-energy X-rays that, according to scientists, could be the "howls" of dead

stars as they feed on stellar companions.

"We can see a completely new component of the center of our galaxy with NuSTAR's images," said Kerstin

Perez of Columbia University in New York, lead author of a new report on the findings in the journal Nature.

"We can't definitively explain the X-ray signal yet -- it's a mystery. More work needs to be done."

The center of our Milky Way galaxy is bustling with young and old stars, smaller black holes and other

varieties of stellar corpses – all swarming around a supermassive black hole called Sagittarius A*.

NuSTAR, launched into space in 2012, is the first telescope capable of capturing crisp images of this frenzied

region in high-energy X-rays. The new images show a region around the supermassive black hole about 40

light-years across. Astronomers were surprised by the pictures, which reveal an unexpected haze of high-

energy X-rays dominating the usual stellar activity.

"Almost anything that can emit X-rays is in the galactic center," said Perez. "The area is crowded with low-

energy X-ray sources, but their emission is very faint when you examine it at the energies that NuSTAR

observes, so the new signal stands out."

Astronomers have four potential theories to explain the baffling X-ray glow, three of which involve different

classes of stellar corpses. When stars die, they don't always go quietly into the night. Unlike stars like our sun,

collapsed dead stars that belong to stellar pairs, or binaries, can siphon matter from their companions. This

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zombie-like "feeding" process differs depending on the nature of the normal star, but the result may be an

eruption of X-rays.

According to one theory, a type of stellar zombie called a pulsar could be at work. Pulsars are the collapsed

remains of stars that exploded in supernova blasts. They can spin extremely fast and send out intense beams

of radiation. As the pulsars spin, the beams sweep across the sky, sometimes intercepting the Earth, like

lighthouse beacons.

"We may be witnessing the beacons of a hitherto hidden population of pulsars in the galactic center," said co-

author Fiona Harrison of the California Institute of Technology (Caltech) in Pasadena, and principal investigator

of NuSTAR. "This would mean there is something special about the environment in the very center of our

galaxy."

Other possible culprits include heavy-set stellar corpses called white dwarfs, which are the collapsed, burned-

out remains of stars not massive enough to explode in supernovae. Our sun is such a star, and is destined to

become a white dwarf in about five billion years. Because these white dwarfs are much denser than they were

in their youth, they have stronger gravity and can produce higher-energy X-rays than normal. Another theory

points to small black holes that slowly feed off their companion stars, radiating X-rays as material plummets

down into their bottomless pits.

Alternatively, the source of the high-energy X-rays might not be stellar corpses at all, astronomers say, but

rather a diffuse haze of charged particles, called cosmic rays. The cosmic rays might originate from the

supermassive black hole at the center of the galaxy as it devours material. When the cosmic rays interact with

surrounding, dense gas, they emit X-rays.

However, none of these theories match what is known from previous research, leaving the astronomers largely

stumped.

"This new result just reminds us that the galactic center is a bizarre place," said co-author Chuck Hailey of

Columbia University. "In the same way people behave differently walking on the street instead of jammed on a

crowded rush hour subway, stellar objects exhibit weird behavior when crammed in close quarters near the

supermassive black hole."

The team says more observations are planned. Until then, theorists will be busy exploring the above scenarios

or coming up with new models to explain what could be giving off the puzzling high-energy X-ray glow.

"Every time that we build small telescopes like NuSTAR, which improve our view of the cosmos in a particular

wavelength band, we can expect surprises like this," said Paul Hertz, the astrophysics division director at NASA

Headquarters in Washington.

Source: NASA Return to Contents

NuSTAR

Source: NASA

Return to Contents

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The Night Sky

Source: Sky and Telescope Return to Contents

By dawn, the Moon, Saturn, and Scorpius have tipped way over in their nightly journey to the southwest.

Tuesday, May 5

Look low in the northeast in twilight for the rising of Vega, the "Summer Star." By nightfall Vega

shines higher in better view. As it gains altitude it grows to be the equal of Arcturus, the "Spring Star"

very high in the east (far to the upper right). They're both magnitude zero.

Wednesday, May 6

Summer is more than six weeks away, but the Summer Triangle is beginning to make its appearance

in the east, one star after another. The first in view is Vega. It's already visible low in the northeast

as twilight fades.

Next up is Deneb, lower left of Vega by two or three fists at arm's length. Deneb takes about an hour

to appear after Vega does, depending on your latitude.

The third is Altair, which shows up far to their lower right around midnight.

Thursday, May 7

Canes Venatici, the Hunting Dogs, floats near the zenith these evenings under the arch of the Big

Dipper's handle.

Friday, May 8

The two brightest points in sky are Venus and Jupiter. At dusk they're in the west and high in the

southwest, respectively. Find the halfway point between them. A little upper right of there is Pollux,

with Castor to its right.

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ISS Sighting Opportunities (from Denver)

No sightings possible in Denver through Friday, May 15, 2015

Sighting information for other cities can be found at NASA’s Satellite Sighting Information

NASA-TV Highlights (all times Eastern Time Zone)

Wednesday, May 6

6:35 a.m. - SpaceX Pad Abort Test (NTV-1 (Public), NTV-2 (Education))

6:35 a.m. - ISS Expedition 43 In-Flight Event with the NBC Today Show and Social Media Questions

with NASA Flight Engineer Scott Kelly (all channels)

Thursday, May 7

10 a.m. - Video File of the ISS Expedition 44 Qualification Training Simulation Runs at Star City, Russia

(NTV-1 (Public), NTV-3 (Media))

10 a.m. - Beating the Odds/Quarterbacks of Life: EFT-1 Student Design Challenge (NTV-2 (Education))

10 a.m. - Video File of the ISS Expedition 44 Qualification Training Simulation Runs at Star City, Russia

(NTV-1 (Public), NTV-3 (Media))

Friday, May 8

9:40 a.m., - ISS Expedition 43 In-Flight Event for ESA for the World Expo in Milan, Italy and a

European Air Chiefs Conference with European Space Agency Flight Engineer Samantha Cristoforetti

(all channels)

3 p.m. - Replay of the ISS Expedition 44 Crew News Conference at Star City, Russia (all channels)

3:50 p.m. - Video File of the Expedition 44 Crew’s Ceremonial Visit to the Gagarin Museum and Red

Square and the Kremlin in Moscow (all channels)

Watch NASA TV online by going to the NASA website. Return to Contents

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Space Calendar

May 05 - Eta Aquarids Meteor Shower Peak

May 05 - Asteroid 2015 HU171 Near-Earth Flyby (0.070 AU)

May 05 - Asteroid 12464 Manhattan Closest Approach To Earth (1.351 AU)

May 05 - Asteroid 159814 Saguaro Closest Approach To Earth (1.491 AU)

May 05 - Asteroid 25275 Jocelynbell Closest Approach To Earth (1.618 AU)

May 06 - Comet P/2004 T1 (LINEAR-NEAT) At Opposition (3.992 AU)

May 06 - Asteroid 2015 HZ Near-Earth Flyby (0.084 AU)

May 06 - Asteroid 10792 Ecuador Closest Approach To Earth (2.163 AU)

May 06 - Asteroid 2597 Arthur Closest Approach To Earth (2.457 AU)

May 06 - Kuiper Belt Object 90568 (2004 GV9) At Opposition (38.409 AU)

May 06 - Jana Ticha's 50th Birthday (1965)

May 07 - Cassini, Titan Flyby

May 07 - Mercury At Its Greatest Eastern Elongation (21 Degrees)

May 07 - Comet 308P/Lagerkvist-Carsenty Perihelion (4.226 AU)

May 07 - Asteroid 2340 Hathor Closest Approach To Earth (0.530 AU)

May 07 - Asteroid 2625 Jack London Closest Approach To Earth (1.096 AU)

May 07 - Asteroid 15092 Beegees Closest Approach To Earth (2.037 AU)

May 07 - Asteroid 15783 Briancox Closest Approach To Earth (3.243 AU)

May 08 - Comet C/2015 F2 (Polonia) Closest Approach To Earth (0.732 AU)

May 08 - Comet 293P/LINEAR Closest Approach To Earth (2.721 AU)

May 08 - Centaur Object 10199 Chariklo Occults 2UCAC 16260366 (14.3 Magnitude Star)

May 09 - Cassini, Distant Flyby of Aegaeon, Daphnis & Telesto

May 09 - Comet 290P/Jager At Opposition (3.168 AU)

May 09 - Asteroid 25930 Spielberg Closest Approach To Earth (1.162 AU)

May 09 - Asteroid 3975 Verdi Closest Approach To Earth (1.999 AU)

May 09 - Asteroid 300221 Brucebills Closest Approach To Earth (2.680 AU)

May 09 - Asteroid 6042 Chesirecat Closest Approach To Earth (3.133 AU)

Source: JPL Space Calendar Return to Contents

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Food for Thought

This Is Your Brain in Deep Space: Could Cosmic Rays Threaten Mars Missions?

NASA aims to get astronauts to the vicinity of Mars by the mid-2030s. Radiation

exposure during the long roundtrip trek could damage astronauts' brains, new

research suggests. Credit: ESA

Mice zapped with cosmic rays can incur brain damage, suggesting that astronauts' mental performance could suffer over time on deep-space missions to Mars and beyond, researchers say.

"There is now cause for concern that cosmic rays can lead to cognitive deficiencies, and this effect is likely to occur in humans as well as rodents," study co-author Charles Limoli, a radiation biologist and neuroscientist at the University of California, Irvine, told Space.com.

As NASA plans for the first manned spaceflight to Mars in two decades or so, scientists want to know what happens to the brains of astronauts exposed to space radiation. "NASA wants to make sure that astronaut minds are up to performing at the best of their capabilities," Limoli said.

Adult brains are more resistant to radiation than other parts of the body, such as the gut and bone marrow, Limoli said. This is because cells in mature brains have stopped dividing for the most part, whereas cells in the gut and bone marrow keep multiplying. When cells that are dividing get hit by radiation, they can accumulate genetic errors that can lead to cancer and other problems.

However, research on the effects of space radiation focuses mostly on high-energy forms of light, such as X-rays and gamma-rays. But a major potential danger to astronauts that has not yet been studied in depth are galactic cosmic rays — massive, high-speed, electrically charged particles emerging from every direction in space. Galactic cosmic rays are caused mostly by exploding stars known as supernovas, and can easily penetrate spacecraft and human skulls.

Astronauts aboard the International Space Station are safe from galactic cosmic rays because they are still protected by the Earth's magnetosphere, which reaches about 35,000 miles (56,000 kilometers) above Earth's surface on the day side. However, astronauts on future deep-space missions farther away from Earth — to Mars or the asteroid belt, for example — face peril from this space radiation.

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"Galactic cosmic rays don't reach the surface of the Earth because the planet's magnetosphere protects us," Limoli said. "It's one reason why we have life on Earth."

In experiments, the scientists bombarded mice at the NASA Space Radiation Laboratory at Brookhaven National Laboratory in New York with beams of the kinds of electrically charged particles that make up galactic cosmic rays — oxygen and titanium ions accelerated "to two-thirds the speed of light," Limoli said.

The mice were genetically altered to have glowing fluorescent neurons in their brains that were easier for the researchers to examine. Six weeks after the rodents were blasted with the destructive particles, the investigators said the mice had fewer dendrites, the branches from neurons that carry the brain's electrical signals. The ions triggered the degradation of these structures that persisted over time.

"I wasn't anticipating such extensive degradation [in response] to relatively small doses of charged particles," Limoli said. "The magnitude of the effect was surprising."

Dendrite loss is linked to mental decline associated with Alzheimer's and other diseases. In tests of learning and memory in which the mice were shown new objects placed in familiar settings, irradiated mice lacked curiosity, were less active in new situations and became confused more easily. If similar changes were to happen in astronauts, it might hinder their ability to respond to unexpected situations or recall information, the researchers said.

Although mental deficits in astronauts from space radiation might take months to manifest, the three years or so required for a round-trip mission to Mars is long enough for such problems to develop, Limoli said.

"Astronauts are expected to do a lot of multitasking, to do experiments, to keep a lot of things straight — and these experiments suggest they might experience performance deficits that might compromise mission activities, and may also face risks to their cognitive health once they return to Earth," Limoli said. "Specifically, what might go wrong is impossible to say, since no one's gone out there yet. I don't think it'd get to the level where astronauts would crash ships because of this, but they might push the wrong button and ruin an experiment."

Moreover, "there is no sign these impairments ever get better," Limoli said. "I would hesitate before using the word 'permanent,' but there is no indication at this time that they do recover."

It remains uncertain if there is anything that can be done to prevent or treat this damage.

"NASA is funding research from me and others to try to develop compounds that can alleviate the effects of radiation on the brain," Limoli said. "Also, if astronauts engage in activities that actively stimulate cognitive function, which might also help mental performance."

A partial solution might involve increasing shielding on spaceships in areas where astronauts rest and sleep. "We are working on ways to minimize this damage in space, and should not let these results discourage our attempts to embark on future deep-space missions," Limoli said.

In the future, the researchers plan to explore the effects of a broader range of galactic cosmic rays to create more accurate simulations of what goes on in space. They would also like to see what happens to mice more than six weeks after they're exposed to cosmic rays.

"The brain is a complicated system — there are many things galactic cosmic rays are doing in the brain that we have yet to discover or understand," Limoli said.

The scientists detailed their findings online May 1 in the journal Science Advances.

Source: Space.com Return to Contents

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Space Image of the Week

Comet Churyumov Gerasimenko in Crescent Image Credit: ESA, Rosetta, NAVCAM; processing by Giuseppe Conzo

Explanation: What's happening to Comet 67P/Churyumov–Gerasimenko? As the 3-km wide comet moves

closer to the Sun, heat causes the nucleus to expel gas and dust. The Rosetta spacecraft arrived at the

comet's craggily double nucleus last July and now is co-orbiting the Sun with the giant dark iceberg. Recent

analysis of data beamed back to Earth from the robotic Rosetta spacecraft has shown that water being

expelled by 67P has a significant difference with water on Earth, indicating that Earth's water could not have

originated from ancient collisions with comets like 67P. Additionally, neither Rosetta nor its Philae lander

detected a magnetic field around the comet nucleus, indicating that magnetism might have been unimportant

in the evolution of the early Solar System.

Comet 67P, shown in a crescent phase in false color, should increase its evaporation rate as it nears its closest

approach to the Sun in 2015 August, when it reaches a Sun distance just a bit further out than the Earth.

Source: NASA APOD Return to Contents