Articles written in Journal of Astrophysics and Astronomy
Volume 38 Issue 2 June 2017 Article ID 0035 Review Article
On 28th September 2015, India launched its first astronomical space observatory AstroSat, successfully. AstroSat carried five astronomy payloads, namely, (i) Cadmium Zinc Telluride Imager (CZTI), (ii) Large Area X-ray Proportional Counter (LAXPC), (iii) Soft X-ray Telescope (SXT), (iv) Ultra Violet Imaging Telescope (UVIT) and (v) Scanning Sky Monitor (SSM) and therefore, has the capability to observe celestial objects in multi-wavelength. Four of the payloads are co-aligned along the positive roll axis of the spacecraft and the remaining one is placed along the positive yaw axis direction. All the payloads are sensitive to bright objects and specifically, require avoiding bright Sun within a safe zone of their bore axes in orbit. Further, there are other operational constraints both from spacecraft side and payloads side which are to be strictly enforced during operations. Even on-orbit spacecraft manoeuvres are constrained to about two of the axes in order to avoid bright Sun within this safe zone and a special constrained manoeuvre is exercised during manoeuvres. The planning and scheduling of the payloads during the Performance Verification (PV) phase was carried out in semi-autonomous/manual mode and a complete automation is exercised for normal phase/Guaranteed Time Observation (GuTO) operations. The process is found to be labour intensive and several operational software tools, encompassing spacecraft sub-systems, on-orbit, domain and environmental constraints, were built-in and interacted with the scheduling tool for appropriate decision-making and science scheduling. The procedural details of the complex scheduling of a multi-wavelength astronomy space observatory and their working in PV phase and in normal/GuTO phases are presented in this paper.
Volume 42 All articles Published: 29 May 2021 Article ID 0023 MISSION
AstroSat is an astronomical observatory from India which is in a low earth orbit of 650 km altitude with a 6-degree inclination and has been functioning successfully in orbit for the last 5 years. The simultaneous observation by the payloads allows imaging of celestial sources in various wavebands that has resulted in scientific achievements which are published in various forum. Uniqueness of its orbit, and scientific objectives calls for a different type of scheduling approach and a hands-free automated tasking of payloads, on this satellite. Several software architectures involving a Centralized data-basecalled Mission Control And Proposals (MCAP) with the Scheduler, AstroSat Scheduler TeRminus for PAyLoads (ASTRAL), AstroSat Scheduler Software for OpeRaTions (ASSORT), Command Sequence Generation (CSG), AstroSat Schedule Viewer (ASV), Astroviewer and AstroSat Long Term Planner(ASPlanner) were developed and used for celestial source observations. This paper describes briefly the scheduling approaches, their goals, utilization, lessons learnt and improvements carried out over the last 5 years.
Volume 42, 2021
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