Arcus:An X-ray Grating Spectrometer on the ISS Mission and Science Overview Randall K. Smith1 1 2 1 3 1 1 4 5 6 1 1 4 A. Foster1 1 2 6 2 7 2 8 2 3 9 10 11 11 1 1 2 2 11 12 13 1
1 2 3 4 5 6 7 8 9 10 11 12 13FAU 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 $125M (FY15). The baseline design uses sub-apertured X-ray silicon pore optics feeding into off-plane gratings to achieve both high spectral resolution with a large effec- tive area. The detector focal plane uses Suzaku-type CCDs. The mission would be ready to be launched and mounted on the ISS in 2020. The mission parameters are R>2500 with >650 cm2 at the critical O VII wavelength around 22-25Å (~0.5 keV), with an overall bandpass from 8-52Å (0.25-1.5 keV), enabling a wide range of science objectives. These values are similar to those of the grating spectrometers considered as part of the proposed Constellation-X and IXO missions, which were highly ranked by two Decadal surveys.
Arcus Science Arcus Design Arcus Optical & Detector Layout To achieve the required Arcus Layout (Deployed) 650 cm2 Optics Module Extendable & Collapsable Science Instrument Module (Mass ~ 120 kg, Star Optical Bench (with shroud) (Mass ~ 20 kg) Arcus uses at least 3 Trackers ~1m x 1m area) Focus Mechanism, ‘petals’ (goal of 4) op- ~500mm 5.5m A/D Electronics, Metering & CCDs Thermo-Elec Cooler Displacement System - Incoming X-rays Radiator with a ~5m focal length ~1m
Optics and off-plane grating O ! Plane Grating Modules Grating Incidence Grazing modules (see right). WiFi Fine DFP Mount Sun Point (opt) Each petal will have an Sensor Power Cabling DFP Mount
TBD (& Data if needed) Point (opt) (Mass ~ 50 kg) individual focal plane Re-closable 2-axis Door Gimbal FRAM (active) FRAM (passive) show in this diagram as a rectangle near the narrow end of
International Space Station each petal. The modular petal design leaves us substantial freedom to arrange the The Arcus mission requirements are similar to those thatwith have optical been pro- posed for the Constellation-X and IXO X-ray grating spectrometers.bench stowed On ISS and other mission re- quirements. Arcus will observe the Ne IX O VIII O VII N VII N VI C VI C V - FoM = [Resolving Power x E#ective Area]$%& (cm) end products of structure Arcus To maximize the low-en- formation in the form of 1000 to complete all of the science planned for IXO. - hot gas beyond the virial 3mÅ - Athena (2028) 5mÅ (Athena systematics limit) radius of galaxies and XMM-Newton RGS NuSTAR. The bench carries with it a shroud for stray light control. A oped for Astro-H and - full-size prototype of this shroud-enclosed bench has undergone over 200 the UW-Madision XQC 100 Chandra Gratings IGM itself via absoprtion Astro-H SXS (shown at right). 5 detection, 500 ksec obs - of Merit Line Detection Figure 10 Using 25 blazar LOS with Fx~10!"" cgs Contamination from other activies on or around the ISS has been a con- Grating Arrays 10 20 30 40 50 cus has the sensitivity to Wavelength (Å) Arcus leverages NASA’s investment in the off-plane gratings - that have been in development at the University of Iowa for than 4mÅ EqW. 10"# Constellation-X and IXO. Off-plane gratings have success- Detecting warm absorbers in AGN Arcus will also direct- Incoming 1 limit in 100 ksec Light Optics Assembly right shows (incl. Gratings) those planned for Arcus have been demonstrated at the NASA/ ) winds from supermassive !" 10"' Arcus in ob- MSFC stray light facility to reach R = Deployable Boom Chandra LETGS/HRC-S warm absorbers with an mounted to the Detectors and size. The gratings 10#& Control Electronics order of magniture more Astro-H/SXS FRAM via a will be housed in sensitivity than Chandra two-axis gim- Star Tracker FRAM modules that will - 10#% Arcus bal system. The Support be paired to the
Detection Threshold (cm Threshold Detection Plate suring the velocity and H EOB system is Internal Metrology N silicon pore optics completely con- System and light-rejecting temporal variations in the “sock” (not shown) - 10#$ ionization structure of the -2 -1 0 1 2 3 4 tained within ing assembly and Log [Ionization Parameter ] jet (see Figure at right). the circular ring Gimbals alignment. 1200 4 Ir-coated SPO petals Arcus will study stellar w/ O"-plane Gratings beneath the op- 96% open Silicon mesh #lter base formation and evolution by 1000 ~1000 cm! Arcus tical layout. ) 45 nm polyimide coating
2 from 9-16Å 70 nm Al optical blocking #lter ~900 cm! Suzaku-type BI CCD QE 800 at O VII onto young stars as well as Silicon Pore Optics - 600 ~575 cm! sitive satellite line diagnos- at C VI Arcus leverages ESA’s investment in the silicon pore optics over the last decade. 400 - tics that require high res- Astro-H SXS Effective Area (cm 200 XMM-Newton RGS as shown at right. Observa- 0 Chandra Gratings 10 20 30 40 50 nonetheless the current generation of 300 tions of Galactic XRB and Silicon Pore Optic Wavelength (Å) - 20 m focal length insights into these systems formance for use in a grating spec- 20 plates 6.5 cm! geo. area Full HEW ~ 24 arcsec 200
Conclusions - m pixel) µ The Arcus science goals were highly regarded both by NASA and by the will be dispersed. These data were from an older mirror module (top left) measured at the 100 The challenge has been to achieve those goals in a timely fashion and an (24 Y Position Transverse HEW affordable cost. Arcus is designed to meet the NWHN recommendations ~ 1 arcsec 0 100 200 300 a SMEX mission by combining existing technology and the opportunities image is basically the geometrical limit. In short: the current silicon pore optics meet X Position (24 µm pixel) provided by the ISS. the Arcus requirement. Data courtesy cosine Research