# Chandrayaan-2 orbiter and lander communications with Earth (IDSN)

In the Seeker video India Could Be the First to Land on the Moon’s South Pole a bit after 04:20 the narrator says:

Okay, well right about now you’re probably wondering how will we be getting any of this information back to us? Well this is where our Vikram lander comes in. Vikram will be in communication with Pragyan, and anything the rover finds will be reported back to Earth via the Indian Deep Space Network.

The orbiter will operate independently with the IDSN, so the team can contact it no matter where it is in its orbit.

I don't quite understand all of this. It sounds like the rover communicates with the lander, and the lander communicates with Earth via the IDSN, without using the orbiter to cache or link.

The orbiter also communicates with IDSN independently, but what does the following phrase mean?

...no matter where it is in its orbit.

If "it" is the orbiter then it seems that the orbiter is in an Earth-synchronous lunar orbit, and I don't think those exist naturally since there's practically no J2.

Perhaps the sentence should be "so the team can contact the lander no matter where the orbiter is in its orbit" instead?

• @WilliamR.Ebenezer thanks for that, I must have missed the "mars" part ;-)
– uhoh
Jul 15 '19 at 7:00
• I have to say, it is now confusing. Now, I'm talking about visibility from the South Pole to IDSN. Might come up with AzEl graph and then follow up with an explainer. But its definitely not a lander-orbit-IDSN primary link, the X-band transmitter size suggests a direct link, so there are two alternatives as far as I can confirm from literature. Aug 21 '19 at 15:17

I think the it refers to Pragyaan. Pragyaan communication is via Lander to IDSN(and DSN) and Lander will have 15 days visibility. Orbiter is in polar orbit of about ~2 Hrs and the orbit is not in anyway earth synchronous. We do experience eclipse and data silence every orbit.

• Let me double check then, the sentence could read The orbiter will operate with the IDSN independently, so the team can contact (the rover for half of each month) no matter where (the orbiter) is in its orbit. for example?
– uhoh
Sep 2 '19 at 3:38
• Yeah but, mission life itself is half month. Not half of every month. Sep 2 '19 at 4:12
• Okay sounds good, thank you!
– uhoh
Sep 2 '19 at 4:14

Your guess seems correct.The Orbiter visibility to the lender is not essential , else lander will need some store and forward system.

• Thank you for you post, and Welcome to Space! A good Stack Exchange answer should cite some sources for statements of fact. Can you add a link or two that support this? It will be helpful to future readers of your answer as well as to me. Thanks!
– uhoh
Jul 21 '19 at 12:03