A signal from venerable space probe Voyager 2 reached Earth today, acknowledging that the spacecraft has received its first command since March 2020 and reset internal clocks as instructed.
Voyager 2 has sent data home since that date, but the ability to send commands to the probe was temporarily offline due to a refresh of DSS 43, the antenna outside the Canberra that thanks to its Southern Hemisphere location, size, and power is the only facility in the world that can reach the spacecraft. DSS 43 is 49 years old and before the refresh many of its major components were more than four decades old. Maintenance requirements were leading to increased downtime so a decision to upgrade the facility was taken.
Work commenced in March 2020 with a scheduled February 2021 completion date that represented Voyager 2 would be out of reach for its terrestrial masters for 11 months, the longest period the probe had been unable to receive commands.
Anxiety about Voyager 2’s state therefore led to an October 2020 exchange that was not much more than a SYN-ACK to prove the probe was still responsive.
The Reg chats with Voyager Imaging Team member Dr Garry E Hunt
Glen Nagle, outreach and visitor centre manager at the Canberra Deep Space Communication Complex that is home to DSS 43, told The Register the October 2020 exchange took place after major work on DSS 43 was complete, but before it had been properly calibrated or commissioned.
The months since have seen commissioning work proceed to ensure the dish can achieve what Nagle described as “hair-width pointing accuracy on a 4,000-tonne moving structure”.
In the small hours of Saturday morning, DSS sent its first command in 11 months to Voyager 2. Nagle said that instruction was to reset an internal clock that, if left to tick over without any signs of action from Earth, would have seen the probe automatically go into sleep mode.
“In the early hours of Monday, we received a signal in which Voyager 2 said it has reset the timer,” he said, after an exchange requiring a 35-hour round trip.
Nagle said that acknowledgement was warmly received by mission scientists, as it was felt that if Voyager 2 entered sleep mode it might prove hard to rouse.
Roses are red
Violets are blue
We’re sending our love
To Voyager 2 ❤️
— CanberraDSN (@CanberraDSN) February 13, 2021
NASA JPL’s Voyager status page says Voyager 2 is currently 18,800,022,000km from Earth and moving at 15.37 kilometres per second. The probe is still running five of its ten instruments, but the Radioisotope Thermoelectric Generator (RTG) that provides it with electricity degrades a little each year. Both Voyagers also rely on their RTGs to keep them warm enough to work.
NASA plans to shut down more instruments to keep the Voyagers online for as long as possible, but the probes look likely to lose touch with Earth in around 2032.
By then, they’ll be 55 years old – half a century longer than the duration of their planned mission. And an even mightier symbol of human ingenuity and curiosity than they are today. ®