The Final Attempt to Contact Pioneer 10

March 6, 2006

In early March 2006, for the very last time the Earth was in a favorable position to receive Pioneer 10's radio signal. It was considered possible that Pioneer 10 would still be able to transmit, despite the age of its electronics, the extreme coldness of deep space, and the diminishing amount of electrical power on board. The Deep Space Network attempted to reacquire Pioneer 10's weak signal, with the hope, however faint, that we may yet have another data point to aid in our investigation of the Pioneers' enigmatic behavior. Pioneer Anomaly Team member Slava Turyshev reports on the outcome of this final attempt to make contact with Pioneer 10.

Update from the Pioneer Anomaly Team

We carried out the observations of the Pioneer 10 spacecraft, per a proposal that was approved by NASA earlier last week, on Friday and Saturday nights, March 3 and 4, 2006 (local time). Sadly, there was no real-time detection of a carrier signal from the spacecraft.

We did carry out open-loop RSR [Radio Science Receiver] recordings of the two passes for archiving. We will process the recordings using parameters that would increase the resolution over the real-time spectral reporting by the receiver, and search for a signal.

At this time, our team does not suspect any errors in our planning, pointing, uplink strategy, or ground receivers tuning predictions, which would explain Pioneer 10's silence. If the signal is not detected in the post-pass processing then we speculate that spacecraft components have degraded faster than was thought, or perhaps the RTG [Radioisotope Thermoelectric Generator] output was no longer sufficient to power the S-band TWT [Traveling Wave Tube] amplifier. This is likely the end of this part of the Pioneer 10 story.

We are now almost ready to start analysis of the entire data set that was recently assembled at JPL.

It would have taken a whole day for the signal to make the round trip... so there will be some delay associated with this.

Why are they trying to contact Pionner?

Is the situation such that Pioneer's (both of them) power supply has dropped too low to send out a signal, or is it such that that Pioneer is too far away and the signal too weak for our largest antennas to pick it up anymore.

It was my understanding that it is the latter, and that if we had a larger DSN dish we would still be able to pick it up (this is ignoring alignments). Am I misunderstanding? Thanks!

We think that the signal actually never left the spacecraft... See, our
figures for required power to operate the transmitter are

Cable loss: 1.6 W
Inverter loss: 5.3 W
CTRF loss: 8.5 W
CTRF load: 12.4 W
TRF loss: 3.4 W
TRF load: 3.6 W
Shunt: 1.6 W
TWT: 22.3 W
-------
total 58.7 W

Thus, we needed total of 58.7 W power to operate the phase-lock loop at
the spacecraft. At the same time, the actual RTG power is about 56.7 W,
leaving us with a 2 W discrepancy, which is consistent with observed
discrepancies in past readings.

Our logic to still conduct this experiment was: i) this was the last
ever attempt, and ii) all the numbers above are with some errors, so the
hope was that we would have just enough power to initiate the contact.
Unfortunately, the cold of the deep space frozen the craft prohibited us
to "motivate" the craft for one last "phone call home.." .

I sent your question to Slava, and here's the response I got:
--Emily