Wednesday, July 31, 2013

ISRO Rendezvous & Docking experiment Update

As mentioned previously on this blog, ISRO has been working on a rendezvous and docking (RVD) experiment mission involving two IMS (Indian Micro Satellite) series spacecrafts. ISAC, a ISRO centre, has been involved in developing navigation and guidance algorithm for RVD. In this experiment, two IMS Spacecrafts, one designated as target and the other designated as chaser, will be launched by a PSLV launcher into two slightly different orbits. There will be no communication link between the target and chaser during the far range rendezvous phase in which relative separation between the spacecrafts will be around 50km to 5km range and this phase will be a ground guided phase. In the docking phase of the mission, docking sensors such as Laser Range Finder during the relative separation of 5 km to 0.25km, Docking Camera during the relative separation of 300m to 1m ,Visual Camera for real time imaging during the relative separation of 1m to docking will be used respectively.

For the purpose of testing and verification of vision based docking algorithms before a real world implementation is carried out, ISRO has developed a 3D simulation environment that is being used to simulate docking phase of the mission. A snap of the simulation is presented in the Figure below.

3D Simulation of Chaser and Target to test vision based RVD. (credit ISRO, [1])
Targeted Applications of RVD: RVD technology is one of many enabling technologies for ISRO's human space flight program. Another promising application of this technology will be increasing age of ISRO's satellites like that from IRS, INSAT and IRNSS systems. RVD technology will allow a resupply (fuel, power pack etc) spacecraft to dock with a satellite in orbit and allow for replenishment of fuel and power pack, thereby increasing satellites age. To facilitate this, as per my research, ISRO has been designing its newest satellite bus called I-6K, which is a unified bus with modular design ,multi EV panels and scalable structure (Bus module & payload module). A modular design will allow easy and fast replacement of bus module in the orbit by the resupply space craft. The resupply spacecraft might itself be a new bus module (with fuel, power pack etc.) that will dock with the payload module in the orbit after the old bus module undocks. 

I-6K Concept Art.

[1] Gladwin J, et al., Performance Evaluation of a Vision Sensor in 3D Virtual Environment for Rendezvous and Docking Application.

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