SSC CGL 2025 Tier-I · 18 September 2025, Shift 1 · General Awareness · Question 12 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 13 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

Which instrument description on XPoSat is correct?

(a)XSPECT extends POLIX’s polarimetry range to 0.5–20 keV.
(b)POLIX performs X-ray spectroscopy and timing.
(c)XSPECT measures X-ray polarization.
(d)POLIX measures X-ray polarization (8–30 keV) to study black holes.

Answer

Why

Correct — D. XPoSat, launched by ISRO on 1 January 2024, carries two instruments. POLIX (Polarimeter Instrument in X-rays) measures the degree and angle of polarisation of X-rays in the 8–30 keV band.

Its targets include black hole X-ray binaries, pulsars, neutron stars and active galactic nuclei, so option (d) describes it correctly.

Why the others are wrong

(a)
XSPECT extends POLIX’s polarimetry range to 0.5–20 keV. — XSPECT is not a polarimeter. It does X-ray spectroscopy and timing in the 0.8–15 keV band and extends nothing of POLIX's range.
(b)
POLIX performs X-ray spectroscopy and timing. — Spectroscopy and timing is XSPECT's job. POLIX, as its name says, is the polarimeter.
(c)
XSPECT measures X-ray polarization. — Polarisation is POLIX's measurement. XSPECT records the spectra and timing of soft X-rays.

Concept

XPoSat (X-ray Polarimeter Satellite) is India's first X-ray polarimetry mission, and the world's second such observatory after NASA's IXPE (2021). A PSLV launched it from Satish Dhawan Space Centre on 1 January 2024.

POLIX, built by the Raman Research Institute, measures polarisation at 8–30 keV. XSPECT, built by the U R Rao Satellite Centre, records spectra and timing at 0.8–15 keV.

Key facts

XPoSat was launched on 1 January 2024 aboard a PSLV from Sriharikota.
POLIX: X-ray polarimeter, 8–30 keV, built by the Raman Research Institute.
XSPECT: X-ray spectroscopy and timing, 0.8–15 keV, built by the U R Rao Satellite Centre.
XPoSat is India's first X-ray polarimetry mission.

Study next

Aditya-L1 and its halo orbit around the L1 Lagrange pointAstroSat, India's first multi-wavelength space observatory

Common traps

Swapping the two payloads. POLIX is the polarimeter, XSPECT the spectroscopy-and-timing instrument.
Believing XSPECT extends POLIX's polarimetry. The two measure different things.

Here a mission is tested on which payload does what. Aditya-L1 is asked at 14 Sep 2025, 12:30, GA Q.12 (it studies the corona) and in this shift at GA Q.24 (its halo orbit).

Related PYQs

No directly related past PYQ was found.

Topic: Culture — all 246 SSC CGL questions on it, every solved shift.