ISEE-3 Update: First DSN Pass and Spin-up Burn Attempt
The DSN pass last week on 18 June that went from 1:45 to 2:45 Pacific Daylight time was not a success. Here is a recap of the pass activity. The DSN pass started at 1:45 pm PDT. Here is a graphic of the pass through a very nice DSN Now web app.
The pass began with a +/- 3 KHz sweep across frequencies representing the input frequency of transponder A (2090.66) MHz + the Doppler offset + an additional 11.25 KHz that came from our most recent command session. The additional offset is due to thermal and or aging issues with the spacecraft transponder. The sweep is done with a carrier only, no modulation, to get the receiver on the spacecraft to lock to the DSN transmitted signal. The output of transponder A will start to vary in a 240/221 relationship when the carrier is locked. Then ranging can occur. The sweep was unsuccessful in establishing a coherent lock. The sweep rate was 60 Hz/sec. This conforms to the procedure used in 1985 by the DSN for the spacecraft during the ICE comet encounter.
