BENGALURU: The Indian Space Research Organisation (Isro) is preparing for additional docking attempts with its recently (Jan 16) linked satellites, focusing on achieving greater precision in its automated docking capabilities.
M Sankaran, director of the UR Rao Satellite Centre (URSC), which spearheaded the Space Docking Experiment (SpaDeX) told TOI exclusively that the space agency is conducting detailed assessments of the docking accuracy before proceeding with the next phase of experiments.
“We have to gain more information about how accurately we have achieved this docking and how much more accuracy we can achieve,” Sankaran said, emphasising that the actual act of docking is just one aspect of the mission.
“How accurately we are docking is important. We will make an assessment of how accurately we have docked and how much we can improve,” he said.
Small separations
Isro, which launched the Rs 225-crore SpaDeX mission on Dec 30, with two 220kg satellites put in space as separate units, had achieved a peak a inter-satellite distance of 12.8km before initiating a series of mamanoeuvres that eventually culminated in the Jan 16 docking.
Isro employed a petal-based docking system, aligned with international standards including the International Docking System Standard (IDSS).
On whether the fuel remaining on the satellites were sufficient to carry out more docking attempts, Sankaran said that for the upcoming trials, Isro plans to separate the satellites by shorter distances, potentially not exceeding 100 metres, unlike the initial approach.
“Fuel consumption won’t be a constraint for these experiments, as the focus will be on perfecting the final approach and docking mechanism rather than long-range maneuvers,” Sankaran said.
Sensors & Sat Capture
The success of these operations relies on a sophisticated array of five different types of sensors, each activated at specific ranges. These sensors, which were evaluated at each step in the run-up to Isro’s first successful attempt on Jan 16, are crucial to both the rendezvous and the eventual docking.
The Proximity and Docking Sensor (PDS) becomes operational from 20 meters, while other sensors work at varying distances – some at long range, others at 200 meters, and some specifically for close proximity operations.
The final phase of docking involves specialised mechanism entry sensors that detect when one satellite’s petals enter the other satellite’s mechanism.
“…After it enters, we have to trigger mechanisms to grab the satellite. Once it is entered, it should get trapped there. It should not go out,” Sankaran explained.
Currently, Isro’s team is analysing data from the successful docking and running simulations to prepare for the next attempt. While the exact timeline for satellite separation remains under review, Sankaran indicated it would take “a few days” as they carefully evaluate their options.
Mastery & future missions
The decision to activate the satellites’ payloads between docking attempts remains flexible.
“If we can do what we want to do immediately, we will do those things and then turn on the payload later. If that is going to take time, then we will turn on the payload and go ahead with the other observations. When we are ready, we will do the docking experiment again,” he added.
As reported by TOI, the successful docking achieved by Isro was the first step towards mastering the technology, which will have to be done multiple times in different configurations, before Isro could confidently use it for future missions like Chandrayaan-4 and India’s own space station.
And, the planned additional trials will help Isro decide how future docking experiments are designed. For Chandrayaan-4, which requires docking to bring back samples, Isro will be operating spacecraft of different sizes, while docking for the space station would have different challenges.
