# When NASA spacecraft arrive at Mars, is Mars always always above the horizon in the US?

Writing How long did the plasma blackouts of Perseverance's signals to MRO and direct-to-Earth last during its seven minutes of terror? I noticed that Mars was high in the sky over the Green Bank observatory near the East coast of the US when the spacecraft arrived at Mars, and this was also the case for Insight's arrival. This allows Green Bank to receive VHF tones from a low gain antenna directly to monitor the Doppler shift and some minimal spacecraft health data during the critical period when the normal high data rate links are difficult or impossible.

This led me to wonder if it has always been the case.

Question: When NASA spacecraft arrive at Mars for orbital insertion or landing is Mars always always above the horizon in the US?

I haven't asked about gravitational assists near Mars because the trajectory is known or predictable well ahead of time and there are no critical events involved during the flyby itself.

• They communicate with Mars-based missions using the DSN and the DSN has ground stations in Spain, the US, and Australia. So they can communicate with the spacecraft no matter when it arrives, in principle. I am guessing they time things such that the arrival or a critical, PR-related maneuver occurs during normal business hours in the US for live viewing. Feb 24, 2021 at 15:28
• @honeste_vivere Please check that I've explained in the question why I think Mars will be visible from the US at landing time.
– uhoh
Feb 24, 2021 at 21:14
• Jeez, I really need to stop rushing my comments. Yes, the question is well posed ;) Feb 24, 2021 at 21:32

Easy enough to verify by computing the Alt/Az of Mars on the descent date/time of NASA spacecraft. I picked a few, got the descent times from Wikipedia, and generated the Alt from Cape Canaveral using JPL Horizons. The command center may have been different places, but they all certainly weren't "high in the sky".

Perseverance
2021-Feb-18 20:55  Alt: 63.683904

InSight
2018-Nov-26 19:52  Alt: 23.700553

Curiosity
2012-Aug-06 05:17  Alt:-26.760763

Phoenix
2008-May-25 23:53  Alt: 61.245107

Opportunity
2004-Jan-25 05:05  Alt: -1.774193

Spirit
2004-Jan-04 04:35  Alt:  9.817655

Mars Polar Lander
1999-Dec-03 20:12  Alt: 39.582025

Sojourner
1997-Jul-04 16:56  Alt: -1.626287