Observing APOD

APOD, a chinese CubSat has been in Space since late 2015. One of its satellites carries a VLBI beacon. Since then, several efforts were undertaken to observe APOD.

We have had several attempts in observing APOD with the AuScope antennas in Hobart, Katherine and Yarragadee. Due to the long baselines, the tracks are relatively short. Our attempts here at the University of Tasmania to correlate the data have not really been successful so far. However, in November we will intensively try to collect more data. This includes an optimised tracking (continuous tracking should be possible with our antennas) and the observations themselves. Andreas Hellerschmied from Vienna will visit us and Tim Natusch from Auckland has also agreed to support us by providing the Warkworth antenna. Hoping to report on successful observations soon.

Friday, Nov 11, Mt. Pleasant observatory: tracking tests with Ho26m. Some tests using ISS signal; S-band beacon (2270) clearly detected, stable throughout track. Sattrack worked smoothly after drive PC reboot. Testing AzEl track for APOD of the next day. Found we can only do one side of the track (up to about 30 deg elevation).

Please find detailed descriptions of each experiment (including results in terms of multiband delays computed with fourfit) on the following pages:

• 316a (KeYg, 2016-11-11, 22:15:00 - 22:39:1010 UT)
• 317a (HoHbKe, 2016-11-12, 09:34:00 - 10:15:33 UT)
• 317b (HbKeYg, 2016-11-12, 21:35:00 - 22:09:49 UT)
• 318b (HbKeYg, 2016-11-13, 10:48:30 - 11:14:27 UT)
• 318c (HbHoKe, 2016-11-13, 21:01:00 - 21:26:59 UT)
• 318d (KeYg, 2016-11-13, 22:35:00 - 22:57:55 UT)
• 319a (HbHoKeYg, 2016-11-14, 10:00:00 - 10:40:05 UT)
• 331b (HbKeYg) - not observed
• a332 (HbKeYg, 2016-11-27 16:00:00 - 2016-11-28 16:00:00 UT, 24 h session)

Files (VEX, tracking and satellite orbit data, etc.) related to these sessions are provided on the VieVS server via SFTP:

• sorts@vievs.hg.tuwien.ac.at
• password: Please contact Andreas Hellerschmied, if you need the password
• directory: /home/sorts/apod/2016/

• The tracking files have to be loaded by the antenna control system which takes some time. Therefore, there is a gap of min. 5 minutes between blocks of quasar observations and satellite scans in the schedules
• Basically the S/X APOD signals are visible on an attached spectrum analyzer. This can be used to confirm that the antenna is on source during tracking.

• Antenna control with direct AzEl input.
  • Format: Azimuth Elevation Position_Angle MJD time
    • First line: number of tracking points (integer)
    • Remaining lines: one line per tracking point, TAB delimited, all integers:
    • Azimuth and Elevation are in degrees x 10000, Position_Angle should always be 0 (not used), MJD is the modified Julian Day number, and time is the number of milliseconds since the start of the MJD

Comments:

• Investigating the signal spectra during tracking a periodic variation in the signal amplitude is visible at higher elevations (more pronounced at X-band than in S-band)

• Antenna control with direct AzEl input.
  • Different format than used for KeYgHb
  • There is a scrip to convert AzEl files written in the format used for KeYgHb to the Ho-specific format (still AzEl positions)
  • AzEl values should be within 0 to 360 deg
  • Acc. of both axes: 0.028 deg/sec^2 (very slow!)
    • Set in acceleration.cat for VIE_SCHED
  • Accoridng to Jamie the actual settling time in 2 sec
    • In antenna.cat: set time constants c1=c2=36 sec. This was changes that to 3 sec along with setting the correct acc. to the acceleration.cat
  • Slew speed of both axes: 38 deg/sec (instead of 40 deg/sec as defined in antenna.cat ⇒ Changed it there!)

Comments:

• If the satellite becomes too fast to track (high elevation) the antenna has problems to catch the track again
  • If there is a rise and set section and the satellite is not observable in between =⇒ Only observe one of the sections.