Voyager suffers a power wobble as boffins start the final countdown for Spitzer

Also: four years of preparation + four spacewalks = one working Alpha Magnetic Spectrometer?

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Roundup Welcome to this week's space roundup, with news of a hello to a resurrected instrument, a heart-stopping moment for an old friend and a final farewell to a teenage telescope.

Voyager 2 gives Earthbound engineers a bit of a fright

Something funny happened over the weekend as one of NASA's veteran Voyager probes inadvertently tripped a fault protection routine after drawing a tad too much power from the onboard radioisotope thermoelectric generator (RTG).

A 360 degree rotation of the spacecraft to calibrate its magnetic field instrument didn't execute as planned on 25 January resulting in two systems that draw relatively high amounts of power (in Voyager terms) running at the same time.

The result was an automatic shutdown of the spacecraft's science instruments in order to deal with the deficit. Engineers had managed to turn off one of the high-power systems by yesterday and turn the science instruments back on (although not resumed taking data.) The gang are currently working to bring the old thing back to normal operations.

At least as normal as one can get when operating quite so far away. Voyager 2 is currently approximately 18.5 billion kilometres from Earth. At that distance, communications at the speed of light take around 17 hours to reach the spacecraft and there's another 17 hours for a response to be received.

Engineers are still unsure why there was a delay in the execution of the manoeuvre commands.

The fading power of that RTG (which drops by approximately 4 watts per year) means engineers must perform a careful balancing act of power management. Heaters are needed to stop fuel freezing in the pipes (which would stop the spacecraft from pointing its antenna toward Earth) while also keeping the instruments and electronics alive. Last year, the primary heater for the cosmic ray subsystem was turned off, although the instrument has continued to function.

The probe is very much on borrowed time, but engineers reckon there is every chance it could continue communicating with Earth until the middle of this decade when power levels are expected to drop to the point where transmissions finally stop.

Member of the original Voyager imaging team, Dr Garry Hunt, remarked to The Register "Again this demonstrates the real stars of the Voyager mission are the brilliant engineers, who keep messaging this ageing spacecraft again and again."

We'd have to agree.

Fixing the unfixable: Alpha Magnetic Spectrometer repairs completed

Closer to home, intrepid astronauts Andrew Morgan of NASA and ESA's Luca Parmitano rounded out the last of four spacewalks to repair the International Space Station's (ISS) AMS instrument over the weekend.

The hulking device was delivered on one of the very last Space Shuttle missions to the ISS and was not designed to be repaired in-situ, making the feat all the more impressive.

To be fair to the AMS, it has lasted far beyond its original three-year design life, clocking up years of science before the coolant pumps failed. Keeping cold is essential for the instrument's mission of detecting electrically charged high energy cosmic rays.

The four spacewalks had required the duo to cut eight coolant lines and splice in a new coolant module.

Those following the spacewalk on NASA TV were treated to a heartstopping moment as Parmitano reported to ground controllers that one of the newly spliced lines indicated a possible leak. With the indication showing even after the 'naut had a crack at tightening things up (something with which every amateur plumber will be familiar) ground controllers prepared to move to a back-up plan of bypassing the possible leak.

However, the final bout of tightening appeared to do the job as it turned out. NASA reported that preliminary testing showed the AMS behaving as expected. Science operations are expected to resume by the end of next week and the hard work of the spacewalkers and the team that devised both the tools and procedures to repair the not-repairable should see the instrument last through the remaining life of the ISS.

So. Farewell then, Spitzer

Boffins are in the process of shutting down the veteran Spitzer Space Telescope, one of NASA's four great observatories, the mission of which is due to come to an end on 30 January.

The infrared telescope has put in more than 16 years of service, during which time it spotted planets outside the solar system, snapped a previously unseen ring around Saturn and produced some jaw-dropping infrared images of star formation thanks to its ability to peer through clouds of dust and gas.

The spacecraft ran out of helium coolant, required to chill its instruments, in 2009. However, due to its distance from Earth Spitzer didn't heat up too much and still operates at -244˚C; enough to observe in two infrared wavelengths. However, as Spitzer drifts further from Earth (it currently trails approximately 254 million km on an orbit similar to that of Earth) communications have become progressively trickier as the window for effective upload and downloads narrows.

A decision to snuff out the mission was made in 2016, with close-out due in 2018. Delays in the launch of James Web Space Telescope meant Spitzer received a fifth and final extension, but now the time has come.

"I can genuinely say that no one involved in the mission planning thought we'd be running in 2019," said Lisa Storrie-Lombardi, Spitzer's project manager. "But we have an incredibly robust spacecraft and an incredible team. And we've been lucky. You have to have some luck, because you can't anticipate everything."

And nobody would have anticipated "Spitzer: The Musical"...

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