Ed's ISS TLE Test Page

March 19, 2021 ISS TLE Test

The purpose of this test is to compare International Space Station Two Line Element sources for predicting ISS Transits of the Sun, Moon and Planets. NASA no longer provides ISS Two Line Elements and instead now provides ephemeris data in the form of OEM messages. CelesTrak.com generates TLEs from the NASA OEM data, available here:Supplemental TLE; as well as, providing Current TLE data from space-track.org. These two sources are tested here. Keep in mind this test is a single data point. As time permits, I'll perform additional tests and add them to this page.

A nice high altitude pass for this test.

ISS Pass Overhead

The specific TLEs that were available at the time of this test were:

Current TLE (space-track.org)
1 25544U 98067A   21078.72537037  .00000634  00000+0  19717-4 0  9993
2 25544  51.6447  65.2021 0003403 127.3103 214.1551 15.48916939274728

Sup TLE (Derived from NASA OEM)
1 25544C 98067A   21079.00208333  .00077557  00000-0  14082-2 0   199
2 25544  51.6430  63.8395 0003280 131.1017 314.3748 15.48905661    18

Below are wide and narrow screen shots of the predicted paths and actual path.

ISS TLE Test Paths - Wide

ISS TLE Test Paths - Narrow

Below is a composite image taken from the video.

ISS TLE Test Paths - Narrow

Click play below to see the video of the test.

Assessment: The actual path was slightly closer to the Supplemental TLE prediction, however the actual arrival time was closer to the Current TLE prediction.

Equipment used: Meade 10" F/10 LX200GPS telescope, No Focal Reducer, Watec 902H CCD Video Camera and  KIWI OSD Video Time-inserter connected to a Garmin-18 LVC GPS. Field of View: 7.75' x 5.85' 

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