The Promise of the SPICA Infrared Observatory Marc Audard on behalf of the SPICA Collaboration Ecogia Science meeting, 02.09.2019 FACULTÉ DES SCIENCES Département d'astronomie SPICA science instrument payload The SPICA payload has three main components; the SPICA Telescope Assembly (STA), a 2.5- meter diameter telescope cooled to below 8 K, and the focal plane instrument assembly with the instruments: SAFARI, a far-IR grating spectrometer and imaging polarimeter, and SMI, a mid-IR spectrometer/imager. The instruments also are maintained at cryogenic temperatures to achieve the required background-limited sensitivity. Spacecraft and payload configuration The overall configuration of the SPICA spacecraft is shown in Figure 3-1, with the service module (SVM) below and on the top the payload module (PLM) with the Science Instrument Assembly (SIA), and the Cryogenic Assembly (CRYO) housing the passive and active cooling system for the SIA. The right hand panels in Figure 3-1 show the layout of the instruments and the two Focal Plane Attitude Sensors (FAS #1 and #2, part of the overall spacecraft pointing system) on the telescope optical bench (TOB) and the focal plane layout. The two science instruments together provide continuous spectroscopic coverage over the full 17 to 230 μm domain, with a wavelength resolution R between a few hundred and a thousand, combined with various efficient large area imaging and polarimetry modes at 100, 200 and 350 μm. By inserting a Martin-Puplett interferometer in the SAFARI/SPEC signal path the resolution can be further increased to R~1500-11000, allowing more detailed line profile studies. SMI provides a still higher resolution (R~28000) capability in the 12 to 18 μm window. SMI will also allow efficient, high sensitivity mapping of large areas in the 17 to 36 μm domain (see Figure 1-22). Both instruments utilise state-of-the-art detector technologies, which in combination with the cold 2.5-meter aperture provide the high sensitivity required to fulfil the main science goals (see Figure 1-2). The Far-Infrared instrument SAFARI The SAFARI spectrometer - SPEC With the galaxy evolution science outlined in section 1.1 as its main science driver, the SAFARI/SPEC spectrometer is primarily optimised to achieve the best possible sensitivity, within the bounds of the available resources (thermal, number of detectors, power, mass), at a moderate resolution of R~300, SPICA – An ESA/JAXA missionwith instantaneous coverage over the full 34 to 230 µm range. A secondary driver is the requirement to also study line profiles at higher wavelength resolution, e.g. to discern the in-fall and outflow of matter from active galactic nuclei. This leads to the implementation of an additional high resolution mode using ESA-led mission a Martin-Puplett interferometer to analyse the signal. With this design, the sensitivity of the R~300 SAFARI/LR mode will be about 5 x 10-20 W/m2 (5σ, with large JAXA contribution 1hr) for a TES (Transition Edge Sensor) detector NEP of 2 x 10-19 W/√Hz, compatible with the •‘PLANCK conFiguration’ sensitivity requirement as dictated by the SPICA • Size - ø4.5 m x 5.3 m science drivers (see Table 2-2). The design allows for further improvements in TES performance, • Mass-3450 kg (wet, with margin) these will directly lead to better overall instrument • Mechanical coolers, V-grooves sensitivity. •2.5 meter telescope, < 8K Figure 3-1 The SPICA spacecraft configuration. The scientific instruments are mounted on the – Warm launch optical bench on the rear of the telescope as shown •12 -230 μm spectroscopY in the middle panel. The SPICA instrument focal plane layout is indicated in the right panel. – FIR spectroscopY – SAFARI – MIR imaging spectroscopY – SMI – FIR polarimetrY – B-BoP •Japanese H3 launcher, L2 halo orbit •5 Year goal lifetime Selected as M5 candidate mission 22 Ongoing Phase A Mission Selection Review (Apr 2021) à downselection from 3 to 1 mission Cryogenics to cool telescope and instruments • Active cooling to 4K and 1.7K – Detector modules at 50mK with dedicated mK coolers (SAFARI, B-BOP) • V-grooves – passive cooling to 40K • Detachable support struts 4K JT 20K ST TheThe SPICA ‘sweet spot’ SPICA ‘sweet spot’– –the dusty universethe dusty universe A unique observatory looking through the veils, enabling transformational science 106 reduction in background! <8K SPICA What is so unique? • A COLD, big mirror → true background limited Mid/Far-IR observing >2 orders of magnitude better raw sensitivity than Herschel • A cold, big mirrorà true background limited observing • ~20 to ~350 μm inaccessible for any observatory >2 →orders oF magnitude better raw sensitivitY than the wavelength domain where obscuredHerschel matter shines • ≈20 to ≈350 fillμm theinaccessible For anY blind spot between JWSTobservatorY and ALMA @ R~ few 1000 à fill the blind spot between JWST and ALMA @ R≈ few 1000 SAFARI/SPICA consortium mtg. #17 - mission status overview - P. Roelfsema 3 Figure 3-5 Left: A Martin-Puplett interferometer: a linearly polarised input signal is divided over two arms of the interferometer using a 45° grid. In both arms the beam goes via a flat mirror to a moving and a fixed rooftop and back, thus the polarization rotates 3 times by 90°. This 270° rotated signal from the left arm is transmitted through the grid while from the right arm it is reflected, allowing the recombined beams to interfere. By moving the central rooftop mirrors over a distance Δx an optical path length difference of 8Δx is created between the two arms. The interference pattern, encoded in the polarization of the output signal, can be recorded by the grating module, due to its inherently linear polarization. Right: The SAFARI/HR optical layout. The high resolution mode optics – the Martin-Puplett Interferometer In the high-resolution SAFARI/HR mode the signal is passed through a Martin-Puplett interferometer (Figure 3-5) imposing a modulation on all wavelengths entering SAFARI/SPEC. The resulting interference that occurs between the two beams of the interferometer is then distributed to the grating modules (Figure 3-4) of the four bands and post dispersed by the corresponding grating onto the detectors. When the interferometer is scanned over its full optical displacement each of the detectors will measure a high resolution interferogram convolved with the grating filter function for that particular detector. Upon Fourier transformation, an individual interferogram produces a small bandwidth, high resolution The SPICA instrumentsspectrum. By combining the spectra from individual detectors a full spectrum at high resolution is obtained. In the current design a mechanical displacement of about 3 cm is envisaged, leading, with a folding factor of 8, to a maximum optical displacement of 25 cm. A short section of the mechanism stroke must be devoted to a short double-sided optical path difference measurement to enable phase SMI correction of the interferogram through accurate identification of the zero path difference position. The available Optical Path Difference • LR-CAM –(OPDlarge area low resolution surveYor) yields spectra with a resolution ranging from R~1500 at 230 • 17 – 36 μm, R = 50 µm to as high as– 120R~11000 at the shortest wavelength of 34 µm. • 4 slits (10’ long) with prism The SAFARI/SPEC Focal Plane Unit • Camera mode 10’x12’ FoVThe SAFARI/SPEC Focal Plane Unit (FPU) as it is mounted against • MR – medium resolution mapperthe back of the telescope is shown in Figure 3-6. The beam from the telescope secondary comes from the top left and is sent into the • 18 – 36 μm, R = 1200 instrument via the– pick2300,-off mirror on the top of the instrument box. • 1 slit (1’ long) with gratingFrom there it goes into the Offner relay optics and on to the Beam and Mode Distribution Optics. On the right the Martin-Puplett signal • HR – molecular phYsics/kinematicspath and its moving mirror stage can be seen. Three of the four • 12 – 18 μm, R = 28,000 (grating modules (red:à VLW,33,000) yellow: MW and green: SW) are visible on the bottom, the LW band GM (orange) isSAFARI at the back. Between Figure 3-6 The SAFARI/SPEC • 1 slit (4” long) with immersion gratingthe MW and SW grating modules the cooler unit (grey) is visible. • R≈300 mode à 1hr/5σ focal plane-5-7x10 unit. -20 W/m2 The SAFARI coolers • Martin-Puplett InterFerometer to provide To cool the TES detectors to their 50 mK operating temperature, a dedicated hybrid ADR/Helium sorption cooler is used. The cooler design buildshigh -onR mode (R≈2000 heritage from the Herschel-11000) and Planck missions. B-BoP A full design has already been carried out for• 4 bands instantaneously covering 35 SAFARI, leading to the construction of an Engineering-230 µm 25 Polarization sensitive • Limited imaging capabilitY: 3 pixels on-skY bolometers • 3 bands: 70, 220, 350 μm; simultaneous observations 2.5’x2.5’ An observatory for the community • Observing time: mission will be open For all astronomers – Guaranteed v.s. open time details TBD – Detailed implementation oF e.g. ‘KeY projects’ TBD – Time Allocation Committee • International communitY oversight/cooperation – SPICA collaboration ≡ 3 instruments + overall SPICA (science) consortium – SPICA Science StudY Team (ESA installed) – represents science communitY 6 – Later; Science advisorY committee, SPICA executive board, TAC etc. The SPICA project • Joint ESA-JAXA project – ESA overall responsibilitY – JAXA major partner …instruments also signiFicant partner – Challenging organization – Total mission cost ≈ 1 billion € ‘European’ instruments JAXA ESA 7 Scientific Advisory Board on the basis of scientific merit. The SAB will subsequently ratify the observation programme with the priorities proposed by the TAC. It will also be the role of the SAB to Swiss involvementdefine what should be the proportion of KP in the OT.