MMS1 orbit file error reading

[Former user]

When I tried to plot MMS orbit file on 07 Feb 2017 I get an error message for MMS1. MMS2-MMS4 are OK. I attach the error message and the OVT view with date and SSCweb selection.

Thanks for your help.

Philippe

[Erik Johansson]

I have not been able to reproduce the bug.

If I remember correctly, the error message should normally imply that there is not orbit data for the entire chosen time interval, and for exactly all satellites for which orbit data is currently needed for plotting (via checkboxes). OVT seems to handle it differently/better for beginning and end (min/max time with orbit data) but maybe a data gap can produce this.

What is the "Start", "Interval", "Tracing step" in the "Time Settings" window when you trigger the bug? According to your first image, "Start" seems to be 2017-02-07 00:30:00.

[C. Philippe Escoubet]

I have again the same problem with THEMIS-E (8 years predict) file.

With the same setup if I use: Start: 2020-12-24 00:00:00 Interval: 2d 3h Step: 10 min

I can get the orbit plotted

If I use: Start: 2022-12-24 00:00:00 Interval: 2d 3h Step: 10 min

I get the same error message as above for MMS. I seems that after a certain date I get the error message (the predicted THEMIS-E orbit file should go up to 2024-12-31)

I use the Mac OS version 10.11.6 and OVT 3.0 build 7.

[C. Philippe Escoubet]

I could install ovt on Windows 8.1 and I don't have the above problem. It seems to be a Mac problem then

[Erik Johansson]

Footnote: I assume that "THEMIS-E (8 years predict) file" still means the SSC-based data (online) as the screenshot implies by the prefix "(SSC)" in the satellite name.

Oddly enough, I can still not reproduce it (MacOS 10.10.5). (Note to self: using OVT development install on Mac "dumle"). If you use the SSC online orbit data, then no platform-dependent code (compiled C code) should be involved for the orbits so I would not expect there to be a difference on different platforms (operating systems). That it works on Windows 8.1, but not on Mac 10.11.6 surprises me.

I doubt that it is the the reason, but in theory it could be that the underlying online data from SSC has changed between your tests and mine. OVT caches data that it downloads from SSC in RAM (during a session) and in files on disk between sessions. You could try to delete the corresponding cache files (~/Library/ovt/3.0/cache/sscsats/ on MacOS.), but you must do it when OVT is not running. Probably will not work.

For the record, I add the two screenshots that you (C. Philippe Escoubet) attached in your email on 2017-12-28.

[C. Philippe Escoubet]

Thanks. I emptied the cache and it worked. In fact I renamed the ssscsats directory and created a new ssscsats directory. I did not see new cache files in the new one though so I am not sure it still uses cache.

[Erik Johansson]

That sounds great! I only suggested clearing the cache because it is so easy to try, not because it is likely to work.

OVT should still use cache files for SSC online orbit data. My memory is blurry on the exact implementation by now, but I think it only reads the (SSC) cache files when launching the application, and only writes (SSC) cache files when exiting the application (or possibly instead: when adding/removing the corresponding (SSC) satellite within the GUI). If you have not exited OVT after launching OVT without cache files, then (I think) there should not be any corresponding (SSC) cache files.