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TIFR Astronomy

100 cm Far Infrared Balloon Borne Telescope

The TIFR Infrared Astronomy Group has been carrying out far infrared (FIR) observations using the TIFR 100 cm balloon-borne telescope (T100). The telescope is f/8 Cassegrain system with a 100 cm primary aperture. The secondary mirror is 27 cm in diameter and is vibrated at a frequency of 10 Hz in order to effect sky chopping (for online background subtraction) with an amplitude of ~4.5 arcmin. The FIR telescope is being regularly flown from TIFR Balloon Facility at Hyderabad for studying Galactic star-forming regions at long wavelengths beyond 100 microns. The T100 is one of the largest payload  to be flown by balloon world-wide and weighs about 1000 kg with ballast. This has been indigenously developed at TIFR.

Fig.1: Successfully flown thrice in a span of ~ one year, it's a record for this large complex IR instrument.

T100+FPS was first launched in 1999 and latest on 18 February 2023. From February 2017 to February 2023, the T100+FPS payload was successfully flown five times, and it mapped large regions in the [C II] line and continuum of several Galactic star-forming regions in the fast scanning mode.

The up-gradation of T100 electronics to incorporate a new Japanese 5x5 FPS array is undergoing. T100 with new FPS will be efficient to map large-area with high-spatial (≤40 arcsec) and spectral (R∼10000; ∼30 km/s) resolutions. It will then allow the investigation of gas geometry and dynamics of filaments in Galactic star-forming regions in unprecedented detail. The first light of the upgraded T100+FPS is planned for the near future.

Fig.2: Detector assembly

Fig.3: T100 ready for launch

The T100 along with the FPS tuned to an astrophysically important line of [C II] at 158 microns, was last launched on February 18, 2023, from the TIFR Balloon Facility, Hyderabad, during the summer 2023 flight campaign. The T100 performed as designed with a Japanese FPS at the focal plane. The performance of the FPS system is being investigated using the FIR data collected during the ~6 hours of float at 31.5 km altitude.