With the initial telemetry analysis and checkout phase done, GRIFEX operations has shifted primarily to data generation and mass downlink. GRIFEX’s performance on-orbit has thus far been mostly nominal, allowing us to complete 11 runs of the MARINA payload and downlink the data from 8 runs. The runs are summarized below:
|1||2/11/2015 22:54:26 UTC||28°54’N 76°45’W||Off the coast of Florida||Yes|
|2||2015/02/18 22:45:00 UTC||80°09’N 135°16’W||North Pole||Yes|
|3||2015/02/19 21:51:00 UTC||69°39’S 100°20’E||South Pole||Yes|
|4||2/25/2015 11:22:41 UTC||48°25’N 65°36’W||New Brunswick||Yes|
|5||2015/02/25 14:17:00 UTC||69°54’N, 34°18’E||North of Finland||Yes|
|6||2015/03/11 23:03:00 UTC||79°35’N 128°35’W||North Pole||Yes|
|7||2015/03/30 23:03:44 UTC||[Ann Arbor run]||No|
|8||2015/04/01 00:32:01 UTC||10°02’N, 88°24’W||Off the coast of Nicaragua||Yes|
|9||2015/04/20 00:58:00 UTC||59°14’N, 104°36’W||North Saskatchewan, Canada||No|
|10||2015/04/21 13:57:00 UTC||40°30’N, 96°9’W||Nebraska City, Nebraska||No|
|11||2015/04/25 13:40:00 UTC||31°39’N, 93°18’W||Robeline, Louisiana||No|
In addition to these 11 completions, we occasionally see aborts of payload runs. The “MARINA Exit Status” telemetry point indicates to us the reason for the abort. The most common values of the “MARINA Exit Status” telemetry point are 0 (Success), 255 (Run in progress), and 1, which is one of 17 error codes. Aborts have been happening more often than expected, an issue we think is due to a timing issue in the code that monitors MARINA while it runs. We recently uplinked a patch such that the code will log more data during each run, which will let us better debug these aborts. Other than delaying runs, these aborts have not had any noticeable effect on spacecraft performance.
For our first imaging campaign (runs 1-5, occurring primarily in February), we were targeting primarily the North pole area, with some runs in view of Ann Arbor to let us monitor the payload as it ran, along with one run at the South Pole to give us baseline pixel brightness levels (since the permanent magnet is aligned such that the imager is facing away from the earth at that location, giving us a dark starfield).
Our next imaging campaign (runs 6-8, occurring in March and April) occurred in parallel with catching up on telemetry downlinks, and thus the runs were less frequent. For this set we had another North Pole run, an Ann Arbor run to check performance after 2 aborts, then a run near the equator to try to get a shot of the earth’s limb.
With baseline payload performance established, we are currently ramping up another imaging campaign, aiming for the best image quality possible. We are currently running approximately daily as we iterate to get a location that’s not too bright.
Once again, we’d like to thank Hams tracking GRIFEX – your continued monitoring has helped us respond quickly to software glitches and keep data flowing. We hope to post more updates as we get closer to an optimal MARINA image.
The Operations Team