The fault protection routines programmed into Voyager 1 and 2 were designed to protect the spacecraft in the event of unforeseen circumstances. Such an event occurred in late January, when a rotation maneuver planned to calibrate Voyager 2’s onboard magnetic field instrument failed to occur because an unexpected delay in its execution left two systems consuming high levels of power (in Voyager terms) at the same time, overdrawing the available power supply.
We looked at this event not long after it happened, and noted that within a couple of days, the Voyager team was able to turn off one of the systems and turn the science instruments back on. Normal operations aboard Voyager 2 were announced on March 3, with five operating science instruments that had been turned off once again returning their data. Such autonomous operation is reassuring because Voyager 2 is now going to lose the ability to receive commands from Earth, owing to upgrades to the Deep Space Network in Australia. This is a temporary situation but one that will last the entire 11 months of the upgrade period.
Fortunately, scientists will still be able to receive science data from the craft, which is now 17 billion kilometers from Earth, but they will not be able to send commands to it during this period. The Canberra site is critical to the Voyager interstellar mission because its 70-meter wide antenna is the only one of the three DSN antennae that can communicate with Voyager 2, which is moving relative to the Earth’s orbital plane in such a way that it can only be seen from the southern hemisphere. Thus the California (Goldstone) and Spain (Robledo de Chavela) sites are ruled out, and there is no southern hemisphere antenna other than Canberra’s DSS43 capable of sending S-band signals powerful enough to communicate with Voyager 2.
Image: DSS43 is a 70-meter-wide (230-feet-wide) radio antenna at the Deep Space Network’s Canberra facility in Australia. It is the only antenna that can send commands to the Voyager 2 spacecraft. Credit: NASA/Canberra Deep Space Communication Complex.
The maintenance at DSS43 is essential, because we have communication and navigation needs for missions like the Mars 2020 rover and future exploration plans for both the Moon and Mars including at some point the crewed missions to the Moon in the Artemis program. Canberra has, in addition to the 70-meter dish, three 34-meter antennae that can receive the Voyager 2 signal, but are unable to transmit commands. During the period in question, Voyager 2 will continue to return data, according to Voyager project manager Suzanne Dodd:
“We put the spacecraft back into a state where it will be just fine, assuming that everything goes normally with it during the time that the antenna is down. If things don’t go normally – which is always a possibility, especially with an aging spacecraft – then the onboard fault protection that’s there can handle the situation.”
Expect the work at Canberra to be completed by January of 2021, placing an updated and more reliable antenna back into service and, presumably, continuing the active work managing Voyager 2’s ongoing mission. Better this, engineers reason, than dealing with future unplanned outages as DSS43 ages, while the upgrades will add state-of-the-art technology to the site. Putting all this in perspective is the fact that the dish has been in service for fully 48 years.