Isro, which knows the frequency in which Vikram was supposed to communicate, has been sending different commands every day, hoping to hear back from the lander. So far, there has been no response. It has been using the 32-metre antenna installed in Byalalu, its deep space network centre near Bengaluru. It also tried another route: Trying to get the orbiter to talk with Vikram, but to no avail.
How can Vikram respond?
Vikram is equipped with three transponders and a phased array antenna — the dome type structure on top of it. The lander will have to use these to receive signals, decipher it and talk back. But it has been unable to do so more than 72 hours after it lost contact with the ground stations here. So far Isro has not officially communicated if these systems are in good condition, or, if they have been damaged. Also, these systems will need power to operate, which takes us to the next question.
Does Vikram have power/energy?
The solar panel on Vikram is on the outside of its body and needed no manoeuvre for deployment. Had it landed as planned it would have picked up the Sun's energy and generated power. Besides, Vikram also has a battery system. But it is unclear if the lander is generating power at this point. Isro has not confirmed this yet. A hard landing could have damaged some of these systems, but Isro is still analysing the data, its chairman says.
For how long can Isro try?
As per Isro's pre-launch estimates, the lander was to get clear sunlight only for one lunar day, which is 14 Earth days. So Isro can keep trying until then, or stop before if it has ascertained that the systems have been damaged. After 14 Earth days, there will be a long cold night, which the systems were unlikely to survive even if the landing module had achieved a controlled, soft landing.