8
$\begingroup$

Suppose Mars Odyssey (ODY) and the Mars Reconnaissance Orbiter (MRO) are being tracked by antenna A (just for example) at the Goldstone Deep Space Network complex in MSPA mode.

Is it possible for antennas A and B to track ODY together (creating an array), while at the same time antennas A and C track MRO together (creating another array)?

Improve this question
$\endgroup$
  • $\begingroup$ Nice question (and answer) - I learned a few things here. $\endgroup$ – Chris Oct 11 '16 at 22:37
9
$\begingroup$

If you have three apertures pointed at Mars, then you would array all three for both orbiters. There would be no point in throwing away the signal of one of the orbiters on any of the antennas. You can array four antennas if you like.

The DSN catalog does mention that combining MSPA and arraying is good bit more work for them, so it has to be negotiated with them when planning the mission.

By the way "track" isn't the right word here, since that implies two-way communication for Doppler or range tracking. MSPA supports multiple spacecraft on the receive side, but only one spacecraft on the transmit side, per antenna. You are receiving data from multiple spacecraft simultaneously, not tracking them simultaneously. Again, per antenna.

Improve this answer
$\endgroup$
  • $\begingroup$ @RojinaAdhikary Since you are new to the site, if this post answers your question, please accept it by clicking the gray checkmark to the left. This lets future searchers see that the question has an accepted answer. $\endgroup$ – Organic Marble Oct 12 '16 at 2:46
  • $\begingroup$ This. I don't know what the resultant beamwidth would be, but it's probably a safe bet that it subtends a larger angle than the entire planet Mars when viewed from Earth, so you would indeed be throwing away perfectly usable signal. $\endgroup$ – user Oct 12 '16 at 14:35
  • $\begingroup$ The wavelength at X-band is about 3.5 cm and the antenna diameter is 35 m. So the beam width is on the order of 0.001 radians. So Mars would fit in the beam width at a distance 1000 times its diameter, or about 7 million kilometers. Mars' closest approach is 55 million km, so Mars and all its orbiters easily fit in the beam width. Ka band is ~1 cm, so that gets closer, but Mars still fits. $\endgroup$ – Mark Adler Oct 12 '16 at 14:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.