Featured Image (Credits ISRO)

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.

Monday, July 29, 2013

Coming together of ISRO & NASA

ISRO and NASA are coming together to harness their strengths in building a satellite for a scientific mission. The mission involves measuring and characterization of carbon/biomass distribution on earth. The satellite will carry a Synthetic Aperture Radar (SAR) operating in dual frequency, L and S bands. NASA will contribute L band electronics and ISRO's contribution will be S band electronics. The satellite will most probably be based on ISRO's IRS bus and will be launched using ISRO's workhorse PSLV. This might be just the beginning of what could be a long term relationship between ISRO and NASA, based on the lines of  ISRO and CNES  partnership. 

ISRO has experience of designing dual band (L & S) SAR. Chandrayaan-2 will carrying one such dual band SAR. 

ISRO Dual band (L & S) SAR for CHandrayaan-2 (credit ISRO)

An abstract of a poster about the joint mission:

A Dual-frequency Spaceborne SAR Mission Concept for Carbon Disturbance Measurements and Characterization
Paul A Rosen, Jet Propulsion Laboratory, (Presenter)
Ralph Dubayah, University of Maryland,
Bradford H Hager, Massachusetts Institute of Technology,
Ian Joughin, University of Washington, 
Since the 2007 National Academy of Science “Decadal Survey” report “Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond,” the National Aeronautics and Space Administration (NASA) has been studying concepts for a Synthetic Aperture Radar (SAR) mission to determine Earth change in three disciplines – ecosystems, solid earth, and cryospheric sciences. One of the most promising and original concepts involves an innovative international partnership between NASA and the Indian Space Research Organization (ISRO). Previous NASA concepts had focused on exploiting an L-band array-fed reflector SAR configuration that enabled > 200 km swath at full SAR resolution and full polarimetry simultaneously in order to meet requirements in all three disciplines. The electronics in this design are relatively compact, allowing for straightforward addition of feed array elements at other frequencies. As the partnership concept with ISRO developed, it became clear that flying dual L- and S-band SAR capabilities, with L-band electronics supplied by NASA and S-band electronics by ISRO, would satisfy science and application requirements of the US and India. A dual-frequency fully polarimetric SAR with the potential for global coverage every 12 days would offer unprecedented capability that researchers could exploit in new and exciting ways. The joint NASA/ISRO science requirements being formulated for ecosystems cover biomass disturbance, agriculture, wetlands and coastal processes, alpine vegetation, and high-resolution soil moisture. The two wavelength system has a number of advantages, including extending the sensitivity of biomass change and regrowth measurements to lower levels of biomass, improved classification of vegetation types, and possibilities for improved vegetation structure estimates, as well as mitigation of ionospheric effects. This poster will provide an overview of the conceptual system and highlight some of the anticipated science products.