Astronomy flagships, past and future
by Jeff Foust
|“We at NASA headquarters build our decisions around the recommendations in the decadal survey,” said Hertz.|
For months, the astronomy community in the United States has been eagerly awaiting the final report of the astrophysics decadal survey, known as “Astro2020.” As the name suggests, the study originally expected to publish its final report in 2020 (the previous astrophysics decadal survey report was released in August 2010.) Even before the pandemic, though, it appeared likely the final report would not be ready until the beginning of 2021, a schedule further delayed by the shift to virtual meetings and deliberations since last spring.
The decadal survey report is now expected… soon, maybe. The most recent formal update about the status of the report, issued June 9 by the National Academies, said the final report had been sent out for peer review. “In our previous update we projected pre-publication release of the Survey in June, however this is clearly going to slip,” the survey’s two co-chairs, Fiona Harrison and Robert Kennicutt, wrote. They did not offer a more precise schedule, and as of July 19 the report had not been released.
The astrophysics community is intensely interested in the report because it will make recommendations on priorities for future missions, including large “flagship” missions that have the potential to shape the next generation of the field, as well as smaller missions and ground-based observatories. The delay in the report complicates planning at NASA, which is already working on fiscal year 2023 budget plans even as Congress deliberates on the fiscal year 2022 budget proposal released in May.
“We at NASA headquarters build our decisions around the recommendations in the decadal survey,” said Paul Hertz, director of NASA’s astrophysics division, at a June 29 meeting.
In preparation for the decadal survey, NASA has invested in technology development projects and studies, anticipating potential priorities the report may ultimately recommend, as well as including a “wedge” for future missions in budget projections for the next several years. “It’s my goal that, no matter what they recommend, we’ve already gone two steps in that direction,” he said. “We’ve got a little bit of a head start in the directions that do get recommendations.”
NASA, meanwhile, has its hands full with recommendations from past decadal surveys. That includes a large space telescope finally nearing liftoff, a venerable space telescope that just resumed operations after a month offline, and an airborne observatory facing another political near-death experience.
The James Webb Space Telescope has suffered years of delays and cost overruns that turned it a prime example of how not to run a large spacecraft project. They spawned independent reviews and congressional hearings and general handwringing about what went wrong and why.
In recent months, though, things have been going relatively well for JWST as it completes its final environmental tests and is prepared for shipment to French Guiana. “We’re getting pretty close to the goal line,” Greg Robinson, program director for JWST at NASA headquarters, at a media event in May. “We just need to punch it over.”
|“We want to be sure that we launch exactly when we’re ready, not a day earlier,” said Zurbuchen.|
Since last year, the mission has been working to a launch readiness date of October 31, 2021, a slip of seven months from the previous date largely because of the slowdown in work caused by the pandemic. However, the biggest obstacle to an on-time launch may be the part of the mission most worried the least about: the launch itself.
As part of the European Space Agency’s contribution to JWST, the agency is providing the spacecraft’s launch on an Ariane 5. That vehicle has long been one of the most reliable vehicles in operation, last suffering a total launch failure in 2002. Given that experience, it seemed like the multibillion-dollar telescope would be in safe hands and launch as soon as it is ready.
However, officials with Arianespace acknowledged in May that there had been an issue with the two previous Ariane 5 launches in 2020. The company said that “post-flight analyses conducted on two recent Ariane 5 launches have indicated the occurrence of a less than fully nominal separation of the fairing, however with no adverse impact on the Ariane 5 flights in question.”
Those two launches took place in February and August of last year, and while successful, in both cases the payload fairing separation system imparted higher loads on the payloads than designed. Engineers have worked for months since the August 2020 flight to correct the problem.
Both Arianespace and ESA now seem satisfied the problem has been corrected. ESA announced July 1 that they completed a final mission analysis review for JWST’s launch. “All technical evaluations performed by Arianespace on the mission’s key aspects, including the launch trajectory and payload separation, have shown positive results,” ESA said in a statement.
The Ariane 5 set to return to service July 27 with the launch of two communications satellites. That is the first of two launches scheduled before the rocket launches JWST. That schedule makes it unlikely that JWST will launch at the end of October given the pace of launch operations. Robinson said in May that he expected the JWST launch to take place about four months after the first of the two preceding launches, which would push it back to late November.
Unlike planetary missions, JWST does not have a narrow period when it must launch to reach its destination, the Earth-Sun L-2 point 1.5 million kilometers away. Launch opportunities for the mission exist nearly every day. Arianespace has reserved a launch period at the spaceport in French Guiana through early December.
“We want to be sure that we launch exactly when we’re ready, not a day earlier,” said Thomas Zurbuchen, NASA associate administrator for science, at an ESA briefing about the upcoming launch in early June. “That is, when the spacecraft is ready and when the rocket and the fairing and everything is ready.”
As NASA prepares the next great observatory for launch, the agency’s classic space telescope is back after a computer problem took it offline for more than a month.
On June 13, a payload computer on the Hubble Space Telescope malfunctioned, suspending science operations. That computer manages operations of Hubble’s science instruments, forcing them to halt even as the rest of the telescope continued to operate normally.
|“We’re continuing to plan for the very long term,” said Space Telescope Science Institute’s Levenson.|
As the outage extended from days to weeks, some in the general public, and even some astronomers, worried if it was a question not when Hubble would resume service, but if. The telescope has been in orbit for 31 years and was last serviced by the shuttle in 2009. At some point something on Hubble will malfunction and with no means (and no budget) to fix it, its operations will come to an end.
NASA officials said the slow process to fix Hubble was, in effect, a technological version of the old maxim to first do no harm. “I have given the Hubble team very clear direction that returning Hubble safely to service and not unintentionally doing any harm to the system is the highest priority, not speed,” Hertz said at the June 29 meeting. “They’re being very deliberate in their analysis and their choices of what they do.”
For weeks, engineers analyzed data and looked at potential causes. They discarded an initial diagnosis of a faulty memory module and later focused on other electronics components within the payload computer. By July 14, a month after the problem took place, engineers concluded that the most likely cause of the malfunction was a power control unit that regulates voltage for the payload computer.
With no way to reset the power control unit from the ground, controllers switched to a backup Science Instrument Command and Data Handling unit with a separate power control unit. Two days later, the swap was complete and, the next day, Hubble was back in service.
“I’m proud of the Hubble team, from current members to Hubble alumni who stepped in to lend their support and expertise,” NASA administrator Bill Nelson said in a statement Saturday after the telescope’s recovery was complete. “Thanks to their dedication and thoughtful work, Hubble will continue to build on its 31-year legacy, broadening our horizons with its view of the universe.”
The incident is a reminder that Hubble’s life is not infinite, but officials remain optimistic that Hubble can operate well into the decade. “We’re continuing to plan for the very long term,” Nancy Levenson, deputy director of the Space Telescope Science Institute, said at last month’s meeting of the American Astronomical Society. One example she gave was an initiative to extend the life of one of Hubble’s instruments, the Cosmic Origins Spectrograph, through the end of the decade.
Another flagship NASA astronomy mission isn’t a spacecraft at all: the Stratospheric Observatory for Infrared Astronomy (SOFIA) is a modified Boeing 747 with a 2.5-meter telescope mounted in the back, designed to operate in flight above much of the atmosphere’s infrared-absorbing water vapor.
SOFIA, though, has struggled to find its scientific footing even after several years of operations, with complaints that its scientific merit didn’t justify its operating costs. NASA directed studies that, by early last year, resulted in recommendations intended to improve its scientific efficiency.
That didn’t stop the administration, though, from proposing to cancel SOFIA in its fiscal year 2021 budget request. “Dramatic improvement in SOFIA’s scientific productivity is not expected,” the agency said in its budget documents. Congress, though, rejected that proposal, fully funding SOFIA in the final 2021 budget.
|“We’ve been in this place before where the president doesn’t have us in the budget,” said Meixner. “We are planning for success.”|
Despite that rejection, and a change of presidential administrations, NASA tried again to cancel SOFIA in its fiscal year 2022 budget proposal in May (see “An aggressive budget for more than just Earth science,” The Space Review, June 1, 2021), for the same reason. “The nature of the program, which relies on observations using an expensive platform with expensive consumables, results in low cost efficiency compared to most observatories,” the budget proposal stated. Among current NASA astrophysics missions, only Hubble has a higher annual operating budget, although JWST will exceed it once it is in service.
SOFIA, which was grounded for several months last year because of the pandemic, and later by aircraft maintenance in Germany, only resumed regular observing flights earlier this year. Observatory officials said last month that they were confident that, once again, Congress would restore its funding.
“We’ve been in this place before where the president doesn’t have us in the budget,” said Margaret Meixner, director of SOFIA science mission operations at the SOFIA Science Center, during the American Astronomical Society meeting last month. “We are planning for success.” That included, she said, preparations for a new series of observations, called Cycle 9, set to start in July, and which would include a deployment of the California-based SOFIA to French Polynesia for observations of objects in the southern hemisphere.
That confidence appears to be well-placed. Last week, the House Appropriations Committee marked up its version of a fiscal year 2022 spending bill. It restored funding for SOFIA, providing it with its full budget of $85 million. “SOFIA can undertake astronomical observations not possible with other ground-based or space-based telescopes available today,” the report accompanying the bill stated.
Now astronomers will wait to see what priorities for future space observatories the decadal survey report recommends. Hertz said in late June he had no knowledge of when that report will be released but thought it would be released sometime later this summer, or this fall. Maybe.
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