The SpicA FAR infrared Instrument (SAFARI), provided by an Dutch consortium lead by SRON, covers the 30-210 µm waveband with a spectral resolution of R ~10 to 10 000, and a field of view of 2' x 2'. The baseline optical configuration of Safari is a Mach-Zehnder imaging Fourier Transform Spectrometer. The principal advantages of this type of spectrometer for Safari are the high mapping speed of the FTS due to spatial multiplexing, the ability to incorporate straightforwardly a photometric imaging mode and the operational flexibility to tailor the spectral resolution to the science programme.
The Safari instrument is constituted by:
Safari Instrument - © SRON
- a front optic telescope at 4.5 K,
- an interferometer at 4.5 K. A magnetic bearing mechanism can generate an optical path difference of 134 mm,
- a back optic camera telescope at 4.5 K,
- three detection focal plane assembly with TES detector array (Transition Edge Sensor) from SRON (64x64 pixels for 35 – 60 mm; 38x38 pixels for 60 – 110 mm; 20x20 pixels for 110 – 210 mm). The TES detector scientific signal is acquire with SQUID (Superconducting Quantum Interference Device) sensor. The detection focal planes are cooled at 50 mK using a ³He sorption cooler (300 mK) coupled to a 50 mK Adiabatic Demagnetisation Refrigerator (ADR) from CEA (INAC-SBT)
- different electronics for the control and the readout of the TES detectors (IRAP (ex-CESR)), for the control of the FTS mechanism (TNO), for the control of the 50 mK cooler (CEA-SAP) and for the control, the management and the interface with the satellite of the instrument (INAF-IFSI).
- harness from the warm electronic to the cold instrument at 4.5 K
Safari instrument optical architecture © SRON
50 mK cooler demonstrator © CEA-SBT
TES Detection Electronic Unit © CESR
The French contribution to the Safari instrument consists in the development and delivery to SRON of:
- the 50 mK cooler CEA (INAC-SBT)
- the electronic for the control of the 50 mK cooler (CEA-SAP)
- the electronic for the control and the acquisition of the TES detectors (IRAP (ex-CESR))
The Safari instrument on Spica will exploit the power of Mean Infrared/Far Infrared (MIR/FIR) imaging spectroscopy and photometry to study the dust-enshrouded processes that drive galaxy evolution. Safari will be able to detect the key MIR and FIR lines from distant galaxies and use the MIR/FIR diagnostics that have, or will have, been revealed and calibrated by Spitzer and Herschel, respectively, in the local Universe. At a redshift of z ~ 1 the rest-frame 11 – 35 µm, which is very rich in ionic fine structure as well as H2 rotational lines, moves to 22 – 70 µm and then out to 33 – 105 µm by z ~ 2 and will still be in the SAFARI spectral range out to a z ~ 6.