arcus:an x-ray grating spectrometer on the iss mission and
TRANSCRIPT
Arcus leverages NASA’s investment in the off-plane gratings that have been in development at the University of Iowa for Constellation-X and IXO. Off-plane gratings have success-IXOO\�ÁRZQ�LQ�VXERUELWDO�URFNHW�ÁLJKWV��DQG�GHVLJQV�VLPLODU�WR�those planned for Arcus have been demonstrated at the NASA/MSFC stray light facility to reach R = h 6h�!�������OLPLWHG�E\�WKH�ÀQLWH�VRXUFH�size. The gratings will be housed in modules that will be paired to the silicon pore optics PRGXOHV��VLPSOLI\-ing assembly and alignment.
Arcus will observe the end products of structure formation in the form of hot gas beyond the virial radius of galaxies and FOXVWHUV��DV�ZHOO�DV�GH-WHFWLQJ�ÀODPHQWV�LQ�WKH�IGM itself via absoprtion WR�EDFNJURXQG�$*1��$V�VKRZQ�DW�ULJKW��RQO\�$U-cus has the sensitivity to GHWHFW�ÀODPHQWV�ZLWK�OHVV�than 4mÅ EqW. Arcus will also direct-O\�REVHUYH�IHHGEDFN�DQG�winds from supermassive EODFN�KROHV�LQ�WKH�IRUP�RI�warm absorbers with an order of magniture more sensitivity than Chandra RU�HYHQ�$VWUR�+��PHD-suring the velocity and temporal variations in the ionization structure of the jet (see Figure at right). Arcus will study stellar formation and evolution by GHWHFWLQJ�DFFUHWLRQ�ÁRZV�onto young stars as well as XVLQJ�ZHDN�EXW�KLJKO\�VHQ-sitive satellite line diagnos-tics that require high res-ROXWLRQ�DQG�HIIHFWLYH�DUHD��as shown at right. Observa-tions of Galactic XRB and EODFN�KROH�VRXUFHV�ZLOO�OHQG�insights into these systems DQG�WKH�VWUXFWXUH�RI�WKH�KRW�LQWHUVWHOODU�PHGLXP�DQG�KDOR�RI�WKH�0LON\�:D\��
Arcus Design
Arcus is an X-ray grating spectrometer mission to be deployed on the International Space Station in response to NASA’s Astrophysics Division plan to announce a SMEX call in Fall 2014
with a cost cap of $125M (FY15). The baseline design uses sub-apertured X-ray silicon pore optics feeding into off-plane gratings to achieve both high spectral resolution with a large effec-
tive area. The detector focal plane uses Suzaku-type CCDs. The mission would be ready to be launched and mounted on the ISS in 2020. The mission parameters are R>2500 with >650 cm2
at the critical O VII wavelength around 22-25Å (~0.5 keV), with an overall bandpass from 8-52Å (0.25-1.5 keV), enabling a wide range of science objectives. These values are similar to
those of the grating spectrometers considered as part of the proposed Constellation-X and IXO missions, which were highly ranked by two Decadal surveys.
Arcus:An X-ray Grating Spectrometer on the ISSMission and Science Overview
Randall K. Smith1��5��$OOXUHG1��0��%DXW]2��-D\�$��%RRNELQGHU1��-��%UHJPDQ3��/��%UHQQHPDQ1��1��%ULFNKRXVH1��'��%XUURZV4��9��%XUZLW]5��$��&DUULHU6��3��&KHLPHWV1��3��'DLJQHDX1��$��)DOFRQH4��A. Foster1��0��)UHHPDQ1��5��+HLOPDQQ2��%��+RZOH\6��'��+XHQHPRHUGHU2��-��.DDVWUD7��+��0DUVKDOO2��5��0F(QWDIIHU8��(��0LOOHU2��-��0LOOHU3��5��0XVKRW]N\9��)��3DHUHOV10��
5��3HWUH11��$��3WDN11��.��3RSSHQKDHJHU1��3��5HLG1��0��6FKDWWHQEHUJ2��1��6FKXO]2��/��9DOHQFLF11��5��:LOOLQJDOH12��-��:LOPV13��6��:RON1
16PLWKVRQLDQ�$VWURSK\VLFDO�2EVHUYDWRU\��20,7��38��0LFKLJDQ��43HQQ�6WDWH�8QLY���503(��6/RFNKHHG�0DUWLQ��76521��88��,RZD��98��0DU\ODQG��10&ROXPELD�8���111$6$�*6)&��128��/HLFHVWHU��13FAU
Arcus Optical & Detector Layout
10 20 30 40 50Wavelength (Å)
0
200
400
600
800
1000
1200
Effe
ctive
Are
a (c
m2 )
XMM-Newton RGSChandra Gratings
Astro-H SXS
Arcus~900 cm2
at O VII
~575 cm2 at C VI
~1000 cm2 from 9-16Å
4 Ir-coated SPO petals w/ O"-plane Gratings 96% open Silicon mesh #lter base 45 nm polyimide coating 70 nm Al optical blocking #lter Suzaku-type BI CCD QE
Conclusions
The Arcus science goals were highly regarded both by NASA and by the FRPPXQLW\��DV�UHÁHFWHG�E\�WKHLU�PHQWLRQ�LQ�WKH������1HZ�:RUOGV��1HZ�+RUL]RQV�'HFDGDO�6XUYH\��:LWK�(6$·V�GHFLVLRQ�WR�ODXQFK�$WKHQD�LQ������DV�WKHLU�/��PLVVLRQ��WKH�JUDWLQJ�VFLHQFH�UHPDLQV�DQ�H[FLWLQJ�RSSRUWXQLW\���The challenge has been to achieve those goals in a timely fashion and an affordable cost. Arcus is designed to meet the NWHN recommendations DQG�FXUUHQW�FRQVWUDLQWV�DW�DQ�H[WUHPHO\�DWWUDFWLYH�FRVW�WKDW�FDQ�EH�ÀW�ZLWKLQ�a SMEX mission by combining existing technology and the opportunities provided by the ISS.
Arcus leverages ESA’s investment in the silicon pore optics over the last decade. 7KHVH�RSWLFV�DUH�SODQQHG�IRU�XVH�LQ�$WKHQD�LQ�������ZLWK�DQ�LPDJLQJ�36)�UHTXLUH-PHQW�RI��··��DOWKRXJK�WKH�$UFXV�UHTXLUHPHQW�RQ�WKH�RSWLFDO�SHUIRUPDQFH�LV�FORVH�WR��··��:KLOH�LPSURYHPHQWV�LQ�WKH�RYHUDOO�LPDJLQJ�FDSDELOLWLHV�RI�WKH�RSWLFV�FRQWLQXH��nonetheless the current generation of 75/��RSWLFV�KDYH��WKH�UHTXLUHG�SHU-formance for use in a grating spec-WURPHWHU��$V�VKRZQ�LQ�WKH�ÀJXUH�DW�ULJKW��WKH�UHOHYDQW�LVVXH�LV�QRW�WKH�IXOO�36)��EXW�UDWKHU�WKH�QDUURZ�´WUDQV-YHUVHµ�36)�DORQJ�ZLWK�WKH�SKRWRQV�
will be dispersed. These data were from an older mirror module (top left) measured at the IRFDO�SODQH��UHVXOWV�IURP�WKH�FXUUHQW�JHQHUDWLRQ�RI�632�DUH�H[SHFWHG�WR�LPSURYH�$OWKRXJK�WKH�EHVW�PHDVXUHG�+(:�IRU�D�632�PLUURU�LV�DERXW����DUFVHF��WKH�GDWD�VKRZQ�KHUH�DW�ULJKW�ÀQG�D�����DUFVHF�):+0�LQ�WKH���GLPHQVLRQDO�SURMHFWLRQ�IRU�WKH�VKRUW�D[LV��ZKLFK�HTXDWHV�WR�MXVW�OHVV�WKDQ��µ�+(:���%HORZ�WKDW�SULPDU\�*DXVVLDQ��WKHUH�LV�D�VHFRQG�a�··�*DXVVLDQ�ZLWK�OHVV�DUHD���,Q�WKLV�VWXG\��WKH�SUREH�EHDP�KDV�D�GLYHUJHQFH�RI��µ��VR�D��µ�image is basically the geometrical limit. In short: the current silicon pore optics meet
the Arcus requirement.
Silicon Pore Optics
����!����%��������'/���'%�.������ �� �������� ������ �� ����� ��
�'%+�'+%���"% �)"!�
�%���� �'��&���/"!��,�%����%���+&�'"���'�% �!���"-��"% �)"!�-"%�&��
�+%,�/���&"%#)"!���!�&�"��?:�����.��&��!����+&'�%&�'"�=.�,�%����%���+&5���+%,�/�?:��"��'�%"+��������)����"�7��"�����%"+#�'"��!��&'%+�'+%�3���+!��!��5�����&+%����+!��!��&3�,��"��)�&�7��" #"&�)"!�-�'��!�����/���/��
B@?:�� <�����'� ��3�<::�� <� �!5����A��&��4���B;?::�",�%���!�#�&&3���B<?::��'� ���
�������������
��!�� �&&�7��!�%�/��!�"+(�"-�!������-�!��
�&�%,����&��!��� �&&�"!���!�&��%" �%�!���"���"!&�'"� ��&+%��,��"��)�&�7�#%"���&��!��'� #"%���,�%��)"!��!�%�&#"!&��'"����!��!�������+.�
��!�#�&&�A6?<��-�'��B<::�� <����'�%"+��"+'�-�'���B;?::5�A�&���
�'����%�������/����
"-��"�/"+!��&'�%&���&#�%&��'���%���&�&2�"-��"�!"% ���&'�%&����'��"%"!��2�
��#�����!��!�3���&"%#)"!��"�+ !�"��#%�6&�"�����&3��!��,'+%��,&�&�"����""��!�5� �&�%,��������'%"!���&�'����'����!�&�'"� ��&+%��'� #�%�'+%���!���$+����%�+ �&'�'+&�"���"%"!�����&�
��!�#�&&�A6?<��-�'��B<::�� <����'�%"+��"+'�-�'���B;?::5��>�&����
XMM-Newton RGS
Chandra Gratings
Astro-H SXS
O VIII O VII C VINe IX N VII N VI
Athena (2028)
Arcus
5m�detection, 500 ksec obsUsing 25 blazar LOS with Fx~10-11 cgs
5mÅ (Athena systematics limit)
C V
3mÅ
10 20 30 40 50Wavelength (Å)
10
100
1000
Line
Det
ectio
n Fi
gure
of M
erit
FoM = [Resolving Power x E#ective Area]0.5 (cm)
Arcus Science
0 100 300200
100
300
200
X Position (24 µm pixel)
Y Po
sitio
n (2
4 µm
pix
el)
Silicon Pore Optic20 m focal length20 plates 6.5 cm2 geo. area Full HEW
~ 24 arcsec
Transverse HEW ~ 1 arcsec
Data courtesy cosine Research
Arcus
Chandra LETGS/HRC-S
Astro-H/SXS
NH
Det
ectio
n Th
resh
old
(cm
-2)
Log [Ionization Parameter j]-2 -1 0 1 2 3 41017
1018
1019
1020
1021
1m limit in 100 ksecDetecting warm absorbers in AGN
Optics Module
5.5m
Extendable & Collapsable Optical Bench (with shroud)
Arcus Layout (Deployed)
CCDs
Focus Mechanism,A/D Electronics,Thermo-Elec Cooler
~1m
TBD
DFP MountPoint (opt)
DFP MountPoint (opt)
2-axisGimbal
FRAM (active)
FRAM (passive)
International Space StationG
razi
ng In
cide
nce
Opt
ics
O!
Plan
e G
ratin
g M
odul
es
IncomingX-rays
FineSun
Sensor
Re-closableDoor
(Mass ~ 120 kg,~1m x 1m area)
(Mass ~ 20 kg)Science Instrument Module
with opticalbench stowed
~500mm
StarTrackers
Radiator
WiFi
Power Cabling(& Data if needed)
Metering &Displacement System
(Mass ~ 50 kg)
The Arcus mission requirements are similar to those that have been pro-posed for the Constellation-X and IXO X-ray grating spectrometers. On WKH�,66��LVVXHV�RI�PDVV��SRZHU��DQG�GDWD�WUDQVPLVVLRQ�EHFRPH�PXFK�OHVV�GLIÀFXOW��%DVHG�RQ�WKH�1,&(5�GHVLJQ�VWXGLHV��ZH�H[SHFW�DW�OHDVW�����RE-VHUYLQJ�HIÀFLHQF\�GXULQJ�D���\HDU�EDVHOLQH�PLVVLRQ��ZKLFK�ZLOO�HQDEOH�XV�to complete all of the science planned for IXO.$UFXV�ZLOO�XVH�DQ�KLJK�75/�SUHFLVLRQ�RSWLFDO�EHQFK�VLPLODU�WR�WKDW�RI�NuSTAR. The bench carries with it a shroud for stray light control. A full-size prototype of this shroud-enclosed bench has undergone over 200 GHSOR\PHQW�F\FOHV�GXULQJ�JURXQG�WHVWLQJ��/LNH�1X67$5�DQG�$VWUR�+��D�PHWURORJ\�V\VWHP�LV�HPSOR\HG�WR�WUDFN���DQG�FRUUHFW�IRU���UHODWLYH�PRWLRQ�EHWZHHQ�WKH�RSWLFV�DQG�WKH�IRFDO�SODQH�GXH�WR�WKH�VOLJKWO\�ÁH[LEOH�EHQFK�Contamination from other activies on or around the ISS has been a con-FHUQ�IRU�;�UD\�RSWLFV��EXW�UHFHQW�VWXGLHV��H�J��6WHDJDOO�HW�DO��������-65����������VKRZ�WKDW�WKHVH�SUREOHPV�KDYH�ODUJHO\�DEDWHG��H[FHSW�GXULQJ�H[-WHUQDO�GRFNLQJ�RI�SD\ORDGV�DQG�VLPLODU�HYHQWV���7KH�ÀJXUH�DW�right shows Arcus in ob-VHUYLQJ�PRGH��mounted to the FRAM via a two-axis gim-bal system. The EOB system is completely con-tained within the circular ring beneath the op-tical layout.
Grating Arrays
To achieve the required 650 cm2�DUHD�DW�����NH9��Arcus uses at least 3 ‘petals’ (goal of 4) op-WLPDOO\�SDFNHG�ZLWK�VLO-LFRQ�SRUH�RSWLFV��632��with a ~5m focal length and off-plane grating modules (see right).
Each petal will have an individual focal plane GHWHFWRU��FRQVLVWLQJ�RI�D�6X]DNX�W\SH�EDFN�LOOXPLQDWHG�&&'�show in this diagram as a rectangle near the narrow end of each petal. The modular petal design leaves us substantial freedom to arrange the V\VWHP�WR�ÀW�ZLWKLQ�WKH�ISS and other mission re-quirements.
To maximize the low-en-HUJ\�WKURXJKSXW��$U-FXV�UHXVHV�ÀOWHUV�GHYHO-oped for Astro-H and the UW-Madision XQC VRXQGLQJ�URFNHW�SURJUDP�(shown at right).
IncomingLight
Star Tracker
Optics Assembly(incl. Gratings)
Deployable Boom
Detectors andControl Electronics
Internal MetrologySystem and light-rejecting“sock” (not shown)
Gimbals
FRAM Support Plate