| Name: Savarimuthu P |
| Affiliation: Indian Institute of Astrophysics |
| Conference ID: ASI2026_951 |
| Title: Radiometric Calibration of the VELC 5303 Å Channel on Aditya-L1 |
| Abstract Type: Poster |
| Abstract Category: Facilities, Technologies and Data science |
| Author(s) and Co-Author(s) with Affiliation: V. Muthu Priyal(Indian Institute of Astrophysics,Bengaluru-560034,India), Savarimuthu P(Indian Institute of Astrophysics,Bengaluru-560034,India), R. Ramesh(Indian Institute of Astrophysics,Bengaluru-560034,India), Jagdev Singh(Indian Institute of Astrophysics,Bengaluru-560034,India), K. Sasikumar Raja(Indian Institute of Astrophysics,Bengaluru-560034,India) |
| Abstract: Abstract
We present an independent validation of the radiometric calibration of the Visible
Emission Line Coronagraph (VELC) onboard Aditya-L1 for observations of the Fe
XIV 5303 Å solar coronal emission line. Space solar coronagraphs generally use
observations of stars for flux / intensity calibration. Compared to this, the primary
flux calibration in VELC is carried out using measurements of the solar disk itself.
The resulting detector response corresponds to a measured count of approximately
(1.70±0.06)×108
counts s−1A˚−1, consistent with the expected solar flux at 5303 Å at 1
AU. To verify this calibration, deep-space observations of the bright star Sirius-A
were analyzed. Based on its known spectral flux near 5303 Å, the expected detector
count was estimated to be ~19±0.7 counts s−1A˚−1, which agrees well with the
observed value of ~23±0.4 counts s−1A˚−1 obtained with VELC. This close agreement
confirms the reliability of the solar disk based calibration method and supports the
conversion of VELC coronal intensity measurements into absolute physical units. In
addition, the Sirius-A observations were used to characterize the point spread
function of the VELC 5303 Å channel. The observed full width at half maximum is
3.8” compared to the design value of 2.5”. These results demonstrate the robustness
of the VELC calibration and its suitability for quantitative studies of the near-Sun
corona. |
