Koshy George

In-orbit performance of UVIT on ASTROSAT

We present the in-orbit performance and the first results from the ultra-violet Imaging telescope (UVIT) on ASTROSAT. UVIT consists of two identical 38cm coaligned telescopes, one for the FUV channel (130-180nm) and the other for the NUV (200-300nm) and VIS (320-550nm) channels, with a field of view of 28 arcmin. The FUV and the NUV detectors are operated in the high gain photon counting mode whereas the VIS detector is operated in the low gain integration mode. The FUV and NUV channels have filters and gratings, whereas the VIS channel has filters. The ASTROSAT was launched on 28th September 2015. The performance verification of UVIT was carried out after the opening of the UVIT doors on 30th November 2015, till the end of March 2016 within the allotted time of 50 days for calibration. All the on-board systems were found to be working satisfactorily. During the PV phase, the UVIT observed several calibration sources to characterise the instrument and a few objects to demonstrate the capability of the UVIT. The resolution of the UVIT was found to be about 1.4 - 1.7 arcsec in the FUV and NUV. The sensitivity in various filters were calibrated using standard stars (white dwarfs), to estimate the zero-point magnitudes as well as the flux conversion factor. The gratings were also calibrated to estimate their resolution as well as effective area. The sensitivity of the filters were found to be reduced up to 15% with respect to the ground calibrations. The sensitivity variation is monitored on a monthly basis. At the end of the PV phase, the instrument calibration is almost complete and the remaining calibrations will be completed by September 2016. UVIT is all set to roll out science results with its imaging capability with good resolution and large field of view, capability to sample the UV spectral region using different filters and capability to perform variability studies in the UV.

In-orbit Calibrations of the Ultraviolet Imaging Telescope

The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in ASTROSAT, the first Indian Space Observatory. The UVIT instrument has two 375 mm telescopes: one for the far-ultraviolet (FUV) channel (1300–1800 A), and the other for the near-ultraviolet (NUV) channel (2000–3000 A) and the visible (VIS) channel (3200–5500 A). UVIT is primarily designed for simultaneous imaging in the two ultraviolet channels with spatial resolution better than 18, along with provisions for slit-less spectroscopy in the NUV and FUV channels. The results of in-orbit calibrations of UVIT are presented in this paper.

In-orbit performance of UVIT and first results

The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within

Investigating AGN black hole masses and the MBH–σe relation for low surface brightness galaxies

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A HOT COMPANION TO A BLUE STRAGGLER IN NGC 188 AS REVEALED BY THE ULTRA-VIOLET IMAGING TELESCOPE (UVIT) ON ASTROSAT

∼15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of

The Horizontal Branch Population of NGC 1851 as Revealed by the Ultraviolet Imaging Telescope (UVIT)

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