Why the S-Band beacon is blocked just now…

You’ll have read in past blog posts that Mars Express will be (has already started) sending a beacon signal to Earth to enable the mission operations team to monitor the craft. It it continues being received, all is (most likely!) well. If it disappears, this could indicate a problem.

Mars Express orbiting the Red Planet - artist's impression Credit: ESA/Alex Lutkus

Mars Express orbiting the Red Planet – artist’s impression Credit: ESA/Alex Lutkus

The beacon was switched ON at 14:48CEST (ground receive time) and is set to run through to the ‘all clear’ at about 21:30CEST tonight. But there was a loss of signal at 15:27CEST – and this was expected. Spacecraft Operations Engineer Andy Johnstone at ESOC explains why:

The blocked signal is caused by the spacecraft itself!

The Large Gain Antenna (LGA) will be hidden by the spacecraft body or the solar arrays at various periods during the transmission of the beacon today [as the craft moves through various pointings], causing a loss of reception on ground.

We do have a second LGA on top of the spacecraft that could have also been used (between them they are visible from any angle) but we elected not to move the antenna selection switches during the flyby. It is something we only do rarely and decided that, as we are conducting (important!) nominal science during the flyby, we would accept the three blackout periods. It also gives us an opportunity to map the true limits transmit of the LGA – we are always keen to sneak in additional tests and learn more about our spacecraft wherever possible!

Editor’s note: Beacon blackouts will run

  • 15:27-16:15 CEST
  • 17:33-18:32 CEST
  • 21:53-23:09 CEST

Leave a Reply

Your email address will not be published. Required fields are marked *

 

Comment moderation is enabled. Your comment may take some time to appear.