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Information about STEREO-A close approach to Earth, August 2023

Important Notice About Reduced STEREO Science Operations

Update: Communications with the STEREO Behind spacecraft were interrupted on October 1, 2014 immediately after a planned reset of the spacecraft performed as part of a test of the solar conjunction operations described below. The spacecraft telemetry indicated an anomaly in the guidance and control system, but this is still being evaluated. No further communications have been successful since Oct. 1st. Follow this link for more information.


Unexpectedly high temperatures in the high gain antenna feed horns on both STEREO spacecraft will require corrective action in the coming months that will severely limit science operations. The high temperatures are being caused by the small angle between Earth and the Sun as seen from each spacecraft. In other words, pointing the antenna at Earth is putting too much solar heat on the antenna feed horn. To bring down the feed horn temperature, and preserve the spacecraft for years to come, the antennas will be pointed off at an angle from both Earth and the Sun, so that less heat will fall on the feed horns.

Communication will still be possible using one of the antenna side lobes, but the telemetry rate will be extremely low. Only limited instrument operations can be supported while the antennas are off-pointed. No recorder playback will be possible during this time. Only real-time data will be available during the 70 meter Deep Space Network contacts, on the order of a few hours per day. A very low rate telemetry stream from the in situ and radio instruments will be recorded for eventual playback.

Side lobe operations have started on the STEREO Ahead spacecraft, and will start on the Behind spacecraft on December 1, 2014. The two spacecraft will remain in this state for just over a year, with normal operations resuming in January 2016. As has been known since before launch, there will also be a several month period during this time when no communications will be possible with either STEREO spacecraft as they pass behind the Sun, simply due to too much interference from the Sun itself.

More information about the schedule of operations can be found on the STEREO observations calendar page.

There's also a NASA article describing the situation with the STEREO spacecraft during this period, with a question and answer section.

Last Revised: Friday, 07-Nov-2014 22:21:23 UTC
Responsible NASA Official: [email address: Therese.A.Kucera<at>nasa<dot>gov]
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