Precise Orbit Determination and Orbit Prediction for POEM-3 Mission: From Initial Phase Till End-of Mission

PSLV Orbital Experimental Module (POEM), also known as PS4 Orbital Platform (PS4-OP), utilizes the spent fourth stage (PS4) of ISRO’s PSLV launcher to provide a long-duration in-orbit platform for hosting the payloads. In this regard, the POEM-3 was the third mission of the POEM series. ISTRAC/ISRO ground stations at different locations provide Telemetry, Tracking and Command (TTC) services to POEM missions, which require a precise prior knowledge of their orbit in terms of mission operations, generating antenna pointing angle and schedule planning of ground stations. To perform these essential operations, the flight dynamics packages: Satellite Precise Orbit Determination (SPOD), Satellite Precise Orbit Prediction (SPOP), and Orbit Products generation packages are designed and developed by the Flight Dynamics Team at ISRO Telemetry Tracking and Command Network (ISTRAC) as per requirements given by PSLV/ISTRAC project. The software packages are used to carry out POEM series flight dynamics operations on a daily basis from the launch day onwards. PSLV fourth stage was lowered to 350[Formula: see text]km orbit at [Formula: see text] inclination after deploying XPOSAT spacecraft at 650[Formula: see text]km altitude to reach the POEM-3 operational orbit altitude by carrying out PS4 engine restarts twice. The POEM-3 was the first low-altitude mission of the POEM series to ensure its decay within 3 months under the influence of natural forces, mainly the Earth’s atmospheric drag. POEM-3 was also the first mission where Navigation with Indian Constellation (NavIC) data was ON till two days before the re-entry date. Based on NavIC short-arc data [Formula: see text]–10[Formula: see text]min, daily two times Orbit Determination (OD), prediction and product generation were carried out using SPOD and SPOP. The SPOD package iteratively estimates POEM-3 orbit using the least square differential correction method. The orbit propagator used within the SPOD is a high-fidelity orbit propagator, SPOP, which was also being used to generate the ephemeris and re-entry prediction once the orbit determination was carried out.