Satellites and More – 2021 #1

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.

I’ve put together a video montage of satellites I serendipitously recorded during the first half of 2021.  Many of the satellites move across the field as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.

North is up and east is to the left; field size 17′ x 11′

Interestingly, four of the satellites above (2, 9, 12 & 13) are in retrograde orbits, that is their orbital inclination is > 90˚ and their east-west component of motion is towards the west instead of the east. However, one of these retrograde satellites (#12) appears to be orbiting prograde. This is Japan’s GCOM W1 environmental satellite, which is in a sun-synchronous orbit. Now, if you look at the very next satellite in the list (#13) you’ll see that it has very similar orbital elements (retrograde, sun-synchronous), I observed it just 5 days later, and it appears to be orbiting retrograde as you would expect (unlike GCOM W1). This is NASA’s Aqua environmental satellite. GCOM W1 and Aqua have orbital inclinations of 98.2082˚ and 98.2090˚, respectively.

There is also a prograde-orbiting satellite (#5) that appears to be orbiting retrograde. This is OneWeb-0056, a broadband internet satellite that is part of the OneWeb constellation, a competitor to SpaceX’s Starlink satellites. Last summer, I saw this same behavior with OneWeb-0047 which has a very similar orbital inclination to OneWeb-0056 (87.5188˚ and 87.8802˚, respectively).

Apparently, satellites with orbital inclinations within a few degrees of 90˚ (polar orbit) can sometimes appear to move in the opposite sense than their orbital inclination would indicate, when seen from the ground. I suspect that it must have something to do with where the satellite is in the sky and the vector sum of the line-of-sight motion of the satellite and the Earth’s rotation, but I have not yet found an expert who can confirm this or provide another explanation.

Satellite #11 is faint and makes a brief appearance in the extreme lower right corner of the frame. If you don’t look there you’ll miss it!

There were two satellites I was unable to identify, shown in the video below. They are either classified satellites or, more likely, small pieces of space debris that only government agencies are keeping track of. Note that the first unidentifiable satellite was moving in a retrograde (westward) orbit. The second satellite could be CZ-3A satellite debris (2007-003Q), but I think it was moving too fast to be that satellite (range 3,018.9 km, perigee 511.7 km, apogee 37,523.8 km, period 671.13 minutes, inclination 24.9940˚, eccentricity 0.7287013).

Unidentifiable satellites

During this period, I recorded one geosynchronous satellite, JCSAT-3. It is no longer operational. Here is the video, followed by the satellite information, followed by the light curve. As you can see when you watch the video and look at the accompanying light curve, this satellite gradually got brighter as it crossed the tiny 17′ x 11′ field of view of the video camera. Amazing!

Geosynchronous satellite JCSAT-3 moves slowly across the field and slowly brightens
JCSAT-3 brightens as it crosses the field

Occasionally, I record other phenomena of interest. Meteors during this period are described here, and you will find a high energy particle that “zapped” the CCD chip in the middle of the following three consecutive video frames. The red circles identify a spot and a pair of spots located some distance away that “lit up” when the high energy particle hit the chip. Events like this are fairly common, but what’s unusual here is the wide separation of the two regions that lit up.

Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21