Hubble’s Feeling Better, JWST Making Progress

It is not back to normal operations yet, but NASA’s Hubble Space Telescope is on the road to recovery.  The legendary telescope needs three gyroscopes to point it in the right direction to study the universe, but only two are working right now. Engineers have made progress in getting a balky third gyro back in operation, though they want to do a few more tests before Hubble resumes scientific observations. Meanwhile, progress is being made on Hubble’s successor, the James Webb Space Telescope (JWST), as NASA and Northrop Grumman deal with the latest cost overruns and schedule delay. [UPDATE, OCTOBER 27, 2018:  NASA just announced that Hubble resumed normal operations with three functioning gyros late yesterday and completed its first science operations (since October 5) at 2:10 am ET this morning.]

Hubble actually has six gyros, all of which were replaced the last time astronauts aboard a space shuttle paid a visit in 2009.  That was the last of five service calls by the space shuttle.  The shuttle program was terminated in 2011 so there is no opportunity to return to Hubble now.

Only three are needed for scientific operations.  The others are spares.

Three of the six gyros installed in 2009 were one model and three were an improved version.  Two of the older version gyros failed previously.  Hubble had been operating with one old and two new, with the third new version in reserve.  On October 5, the old one gave up the ghost, which was not a surprise to Hubble’s operators.  However, when they turned on the new gyro being held in reserve, it gave anomalous readings, returning “extremely high rotation rates.”  The telescope was put into “safe mode” where it cannot conduct science operations until engineers determine how best to proceed.

Initially they reset the gyro by turning it off and back on again since it had not operated for 7.5 years.  That did not help, unfortunately.  Then they executed a series of spacecraft maneuvers, turning Hubble in opposite directions to clear any blockage in the “float” (the cylinder in which the gyro’s wheel is mounted).  That seems to have done the trick.  Today, they reported that the gyro is now operating in “a normal range.”

The rotation rates produced by the backup gyro have reduced and are now within a normal range. Additional tests to be performed to ensure Hubble can return to science operations with this gyro. For more info: https://t.co/lT2Wpycqw2

— Hubble (@NASAHubble) October 22, 2018

They still want to conduct more tests, though, before returning to science operations.

Hubble was launched in 1990.  During the five service calls, space shuttle astronauts replaced and repaired many of its systems, but it will not last forever.

NASA Astrophysics Division Director Paul Hertz told an advisory committee today that the agency developed contingency plans years ago for when Hubble no longer would have three functioning gyros. At the Astrophysics Advisory Committee (APAC) meeting today, he said Hubble can produce valuable science even with just one gyro.  “What we lose in one-gyro mode is how much of the sky is accessible,” he explained.

Hubble looks at the universe primarily in the visible wavelengths and some infrared. Hubble’s successor is the James Webb Space Telescope (JWST), which is entirely infrared. It will be able to look back further in time than Hubble.  The plan had been for both telescopes to operate at the same time, but JWST’s launch has been delayed again and again with consequent cost overruns. Until recently, it was scheduled for launch this month — October 2018 — at a development cost of $8 billion. Now the launch date is March 2021 with another 10 percent overrun — $803 million — breaching a congressionally imposed cost cap.

What shape Hubble will be in by the time JWST is launched is unknown.

JWST program scientist (formerly program director) Eric Smith told APAC that although the amount of time a fully functioning Hubble and JWST could observe in tandem may be shorter than desired, JWST still should be able to work with two other NASA space telescopes — the small Transiting Exoplanet Survey Satellite (TESS) launched earlier this year and the flagship Wide-Field Infrared Survey Telescope (WFIRST) currently in development — to produce ground-breaking science. NASA is not looking at the JWST delay in terms of whether it will degrade the total amount of science these telescopes can deliver, Smith said, but how to take advantage of the delay to increase that science.

That assumes TESS is extended beyond its nominal two-year lifetime and that WFIRST is built at all.  The Trump Administration proposed cancelling WFIRST in the FY2019 budget request.  NASA is part of the Commerce-Justice-Science (CJS) appropriations bill, which has not cleared Congress yet.  NASA is operating under a Continuing Resolution until December 7 and WFIRST is proceeding pursuant to the FY2018 appropriations act.  In action on the FY2019 CJS bill so far, the House and Senate appropriations committees rejected the Trump proposal and added money to keep WFIRST going, though different amounts.

Those actions came before the extent of the new JWST overrun was made public, however. NASA insists it does not require any more money for JWST in FY2019, but will need $490 million above its planned funding level for FY2020 and FY2021.  (The rest of the money needed to cover the overrun will be reallocated from funds that were intended to pay for JWST operations. That money eventually will have to be replaced, but not for several years.) Hertz could not share internal discussions about where NASA and the White House Office of Management and Budget (OMB) plan to get the $490 million, but he “anticipates a likely impact” on NASA’s other science activities.

NASA created an Independent Review Board (IRB) chaired by Tom Young to look at the causes of these most recent JWST problems and how to solve them. Hertz said the IRB will reconvene at the end of November and beginning of December to review NASA’s new plan and how NASA and JWST’s prime contractor, Northrop Grumman, are implementing its 32 recommendations.  The IRB pointed to “human errors” at Northrop Grumman as the top reason for the overrun.

Smith painted a positive picture of JWST’s progress since the IRB report was completed.  JWST has two parts: the instruments that will study the universe and the spacecraft that houses them. The instruments are fine.  The problems are with the spacecraft.  Smith said it is about to undergo a second set of acoustic tests.  During the first round, about 70 fasteners fell off the sunshield that must protect the instruments from the Sun and keep them very cold, which is necessary for infrared observations.  If this test is successful, Smith said the spacecraft would be back in the “normal flow.”