[seatac76]

They use RTGs[1] as the power and heat source, I think CY3 was just solar powered and did not have thermal protection you get from RTGs for electronics.

[1]https://en.m.wikipedia.org/wiki/Radioisotope_thermoelectric_...

[shauryamanu]

They are still working on RTGs. https://www.thehindubusinessline.com/economy/isro-barc-join-...

Above was paywalled, check this https://www.reddit.com/r/ISRO/comments/151j6zw/isro_barc_joi...