Abstract Details
| Name: Venkata Suresh Narra Affiliation: Indian Institute of Astrophysics Conference ID: ASI2016_914 Title : Surface roughness requirements on primary mirror of Visible Emission Line Coronagraph (VELC) on board INDIA’s ADITYA-L1 mission Authors and Co-Authors : B. Raghavendra Prasad, Indian Institute of Astrophysics Mr. Raj Kumar N, Indian Institute of Astrophysics Jagdev Singh, Indian Institute of Astrophysics Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : Aditya-L1 is India's first space solar mission to be positioned at first Lagrangian (L1) point. Visible Emission Line Coronagraph (VELC), which is an internally occulted mirror coronagraph, is the primary payload of the mission dedicated for solar coronal studies. VELC is designed for simultaneous narrow band spectroscopic observations in emission lines 7892Å (FeXI), 10747Å (FeXII), 5303Å (FeXIV); spectro-polarimetric observations in emission line 10747Å (FeXII) over a Field Of View (FOV) ±1.05Ro-1.5Ro (Ro-solar Radii); and broad band imaging of solar corona at 5000Å over a FOV ±1.05Ro-3Ro. To achieve the scientific goals of the payload, instrument background should be less than 5ppm (parts per million) over the FOV. The instrument background should follow the profile/trend similar to the coronal intensity variation over the FOV. Major contributor to the instrument background is the scatter due to roughness of primary mirror (M1) surface. Current work is focused on modelling of Bi-Directional Scatter Distribution Function (BSDF) and corresponding scatter distribution over the FOV by simulations in order to arrive at the surface roughness specifications of M1. Estimation of roughness correction factor due to finite band width of the profilometer is very important and it should be taken into account prior to specifying the surface roughness requirements of M1. This paper describes in detail the simulations and results. All the simulations are carried out using Advanced System Analysis Program (ASAP). |