AO-40 YACE Pictures

Orbit number 292, June 18, 2001

The YACE (Yet Another Camera Experiment) aboard the AMSAT OSCAR 40 spacecraft was used to take images of Earth to verify the spacecraft's attitude.

Ten pictures were taken at 2 minute intervals. The JPEG quality was Q=25 in order to keep the file size small, and the same Q as was used for Earth images pre-incident. The JPEGs are 256-level (8 bit) greyscale.

Click on the small image to see the full-size image.

Original Despun UTC time MA
17:08:40 1.612
17:10:40 2.064
17:12:40  2.516
17:14:40  2.968
17:16:40 3.420
17:18:40 3.872
17:20:40 4.324
17:22:40 4.776
17:24:40 5.228
17:26:40 5.680

The MA values shown above are based on NORAD Keplerian elements (orbit 294). The IHU-2 clock was checked and was correct within one second. Spin rate was 6.567 rpm. The camera field of view is 20.74 x 20.74.

Comments

1. The spacecraft spins some 46 during the exposure so there is some distortion in the raw images.

2. Despun images are also supplied. The larger cross indicates the spin axis, the smaller cross is the camera image center; the camera boresight is misaligned by 1.35. Thanks to Stacey Mills W4SM for these.

3. The Earth's edge is in some of these images, and the angular distance from the boresight indicates an attitude of alon/alat = 277.3/-1.8 ; accuracy approx +/- 0.2. See the diagram:

4. There is little topography evident in the images; most are of the Atlantic Ocean along the equator. The last few images show the terminator, and this annotated image shows the best of these (the 17:22 UTC image) annotated with various features:

5. The images are much degraded compared with those of before the motor system failure, and possibly indicate a deposit on the lens. There is some evidence that this 'fogging' is reducing as time passes.


Article and analysis by James Miller, G3RUH, June 21, 2001, for the AO-40 command team.