Thursday, April 19, 2018

This 'Blink-And-You-Miss-It' Video Clip Reveals The Future Of India's Space Programme

The house of "Our Lady of Perpetual Excitement" venturing into yet another realm of Space acitvity.

India's Space programme has, over time, been making progressively mature strides, as exemplified by the recent successful launch of its GLSV Mk. II Launch Vehicle's F08 mission. The satellite it successfully deployed, though, has been behaving in unexpected manners. This launch was immediately followed, more recently, by the successful PSLV-C41 mission, just 11 days later, a quick mission turnaround time, something it attempted for the first time. Across the Atlantic Ocean, Arianespace is getting ready to launch India's heaviest satellite, the GSAT-11. Safe to say that ISRO has set, for itself, quite a steep challenge for this year.
Indian Space Programme - Docking And Berthing Experiment

In keeping with this upwards trajectory of realising increasingly challenging technological goals, India & Russia, in 2015, signed a Memorandum of Understanding for "expansion of cooperation in the field of the exploration and use of outer space for peaceful purposes". Signed by the Indian Space Research Organisation [ISRO], on behalf of India, & the Roscosmos State Corporation for Space Activities [ROSCOSMOS], the 2 traditional partners envisage working together on an extensive range of issues including, but not restricted to, improvement & interoperability of IRNSS & GLONASS constellations, development of new Rocket Propulsion systems such as Arcjet Thrusters, Kerosene & LNG Propulsion systems, demonstrating X-ray pulsar-based navigation. Collaboration plans also includes "Development of rendezvous and docking mechanisms compatible with International Space Station (ISS) and ISRO's crew module".
This particular initiative stands out due to the quantum leap-esque nature of the objective. To be fair, plans for future Indian Manned Space mission has been a publicly stated intent, for a long time now. To that end, ISRO has programmes underway to develop its various enabling technologies, including Human-rated Orbiter, to launch into Space, using its LVM3 rocket, where it would orbit the Earth, before re-entry - an undertaking of relatively short-time duration. It has scheduled a Pad Abort Test, later this year, to evaluate the reliability of the Crew module, that will house future Indian Spacefarers. The ability to Rendezvous & Dock [RVD] with an orbiting Space Station, would permit for much longer duration operations in the outer Space, a mission demonstrating a much higher regimen of capability.
A recently released promotional video by the Bengaluru-based ISRO Satellite Centre [ISAC], encapsulating its activities of 2017 [source], shows a brief glimpse of its efforts to develop the necessary RVD mechanism.
This clip is additionally interesting, because it shows two separate RVD mechanisms. At the start of the video, the, then, Chairman of ISRO, A.S. Kiran Kumar, is seen alongside a model of a design based on the low-impact International Berthing and Docking Mechanism [IBDM]. Following that, at around 3 seconds, the video shows a mechanism in action, that involves a Robotic Arm.
IBDM Compatible Design - Indian Space Docking Technology - 01 - TN
The former could be the design being honed for future missions to Space Stations, eventually to one that India itself has developed & launched. ISAC, last year, put out a notice soliciting Expression of Interest for developing a VDE Standard-compliant Test Rig, that could be used to evaluate its IBDM design.
IBDM Compatible Design - Indian Space Docking Technology - 02 - TN
The second design, involving use of Robotic arms lends itself to some speculations.
This design is likely to be the one it is developing as part of ISRO's aim of refuelling & repairing orbiting satellites.
Robotic Arm - Indian Space Docking Experiment Mission - 01
As reported some time back, doing so "will allow ISRO to enhance their lives by refuelling them. It'll also reduce space debris" by reducing the number of satellites needed to be launched, since it can keep the orbiting satellites operational for longer.
Budgetary allocation for this, however, remains extremely "modest". According to the 2016-2017 Union Budget, an amount of Rs. 10 Lakhs [around $15,400 USD; taking $1 USD = Rs. 65 INR] was allocated towards the Space Docking Experiment Mission, coming under ISRO's Space Sciences undertaking, that had an allocation of Rs. 178.95 Crores [$27.5 Million USD] during that period.
Subsequent Budget reports have ceased giving breakup details. However, a simplistic extrapolation would put the 2018-19 allocation to around $19,800 USD [Space Sciences allocation: $35.4 Million USD]. Approaching the time of full-scale realisation of the design, the budgeted amount, currently tethered, will, undoubtedly, have to increase many folds over.
With an eye on reaching that stage, ISRO has planned incremental steps involving, both, physical & simulation experiments to validate the hypothesised concepts & the Engineering solutions. One such experiment described in a paper titled, 'Relative State Vector Generation Algorithm For On-board Navigation For Rendezvous Docking Experiment' would involve,
"two IMS (Indian Micro Satellite) Spacecrafts, one designated as target and the other designated as chaser, are launched by a PSLV launcher into two slightly different orbits. No communication link between the target and chaser during the far range rendezvous phase in which relative separation is around 50km to 5km range is envisaged and this phase is 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 0.25 km, Docking Camera during the relative separation of 300m to 1m, Visual Camera for real time imaging during the relative separation of 1m to docking are used respectively"

This need to perform Docking & Berthing would require, among other things, development of accurate Electro-Optical systems, along with high precision proximity sensors, to achieve error-free RVD. A wide-ranging field of technologies & sysstem of systems would need to be realised & made to work in sync to achieve Mission success. With a view of leveraging the efforts of the Academia, ISRO has reached out to them. In 2017, it initiated a Respond programme, that has listed out the numerous technological challenges, encompassing the entire Spectrum of India's Space programme, that it would like Indian Academia & relevant Institutes to take up.
This includes some issues pertaining to RVD missions. Under the Control & Guidance challenge, it requires that,
"To achieve docking during the final phase of the mission, the relative position and velocity of the target spacecraft and chaser spacecraft has to be brought to zero. To ensure proper alignment of the docking port, the relative angular orientation needs to be precisely aligned. Moreover, relative angular rate of the target and chaser are to be very close to zero for successful docking. Simultaneous control of the translational and rotational dynamics is required to achieve the docking conditions."
In order to navigate & achieve accurate Attitude Control, it requires the,
Design, Development and Qualification of a Fully Autonomous Videometer based high precision relative navigation and attitude reference system for space docking experiment - system consisting of retro reflectors, illuminators, camera, complex image processing algorithms involving state observers, filtering algorithms, etc. for range, range rate, Line Of Sight (LOS), relative attitude determination.
There is also a need to undertake study of the "Orbital dynamics of formation satellites", including formulating the necessary Navigation, Guidance & control algorithms.
With the RVD programme, ISRO is venturing an all-new realm of Space missions. Watch this "Space" for more.