UT Nov 03, 2022: Imaging Satellites

Michael Richmond
Nov 06, 2022

On the night of Nov 02/03, 2022, I observed several artificial satellites of Earth as part of a remote-sensing project. These are preliminary tests of my ability to measure properties of satellites in different types of orbit.

The main setup was:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• clear filter, exptime 1, 2, or 3 seconds (however, I did take domeflats in BVRI as well)
• images binned 4x4
• no guiding
• focus values:
  • clear: 1.045 yielding FWHM 2.8 at T = 52/11
  • B: 1.080 yielding FWHM 3.0 at T = 52/11
  • V: 1.062 yielding FWHM 2.8 at T = 52/11
  • R: 1.045 yielding FWHM 2.7 at T = 52/11
  • I: 1.028 yielding FWHM 2.3 at T = 52/11
• camera ran at T = -20 C

Notes from the night:

• skies were clear, but air was humid. Just as I was closing, a light fog started to appear.
• 9-day waxing gibbous Moon was close to some of my targets
• the seeing was very good

Information on flats:

• domeflat exposures reveal

  
             Filter         exptime        mean counts
           -----------------------------------------------
             clear            3              28,000
              B              30              11,000
              V               6              13,000
              R               6              18,000
              I               6              15,000
           -----------------------------------------------
      

Below are pictures of the master domeflats, shown at 25% of actual size. As you can see, they look very similar, sharing most of the dust donuts (which must therefore be on the dewar window).

clear and B

V and R

I

The first target tonight was GOES-16, a geosynchronous weather satellite. It was close to the Moon at the time of these images. Below is a sample 3-second exposure with the sidereal tracking turned on (as usual).

I turned off the tracking, so that stars drifted past, but the geosynchronous satellite remained motionless. In the 1-second exposure below, the satellite is just below center.

The second target was DIRECTV-15, a geosynchronous communications satellite. Below is a 3-second tracked image. You can see two trails below center.

I turned off the tracking again to capture a 1-second image, shown below. Note that two motionless dots are visible: one is DIRECTV-15, and the other must be another geosynchronous satellite; perhaps another DIRECTV bird.