NASA may change MRO orbit to support Mars 2020

 

NASA's Mars Reconnaissance Orbiter (MRO) could change its orbit to better support the Mars 2020 mission after landing, a shift that could affect its science.

NASA is considering changing the orbit of one of its oldest Mars spacecraft, a move intended to support the Mars 2020 mission after landing but which could affect both its science and support of other missions.

NASA launched the Mars Reconnaissance Orbiter (MRO) in 2005 with a suite of six science instruments, including a high-resolution camera. The spacecraft has increasingly been used as a communications relay, supporting spacecraft on the surface of Mars.

In 2018, concerned about aging components on the spacecraft, NASA proposed a potential change to the spacecraft’s orbit. MRO is currently in a sun-synchronous orbit that passes over surface at midafternoon. NASA proposed shifting the spacecraft into an orbit with a crossing time later in the day to reduce the amount of time in each orbit the spacecraft is in the planet’s shadow. That would reduce the workload on the spacecraft’s batteries and extend their lives.

At the time, NASA said it would defer a decision until after the landings of the InSight mission in November 2018 and Mars 2020 in February 2021. With Mars 2020 now weeks away from landing, that decision on whether to change MRO’s orbit is coming due.

“Our intent is to make a decision following the landing and initial operations of Mars 2020,” Eric Ianson, director of NASA’s Mars Exploration Program, said at a Jan. 27 meeting of the Mars Exploration Program Analysis Group (MEPAG).

While the change in orbit is intended to extend MRO’s life, some Mars scientists are concerned it could disrupt science. The different orbit would make it more difficult to compare new observations with earlier ones. It could also affect MRO’s ability to provide support to other missions, such as the Curiosity rover.

“We want to make sure we fully understand the benefits of staying in the current orbit and adjusting the orbit,” Ianson said. “I think people notionally have an idea about that, but I don’t think we’ve fully examined it and had a really in-depth discussion about it.”

Michael Meyer, lead scientist for the Mars Exploration Program, said at the MEPAG meeting that a potential change in the spacecraft’s orbit could have “a few other complications,” such as support for both Curiosity and the European Space Agency’s ExoMars mission, now scheduled for launch in 2022 after it missed its mid-2020 launch window.

“We’re going to revisit it” after the Mars 2020 landing, he said, “and do what the real trades are, and make a decision on what the best thing is to do for overall Mars science.”

The communications infrastructure at Mars is a growing concern for scientists and mission planners. NASA has relied on orbiters launched primarily for science missions to serve as relays, including MRO as well as Mars Odyssey, launched in 2001, and MAVEN, launched in 2013.

Proposals in recent years for new orbiter missions either devoted to communications or with communications as one of their primary roles have made little progress. The most recent concept, presented at meetings in late 2020, called for a network of three satellites with intersatellite links to provide continuous high-bandwidth communications for spacecraft both on the surface and in orbit. Those spacecraft could be developed in some kind of commercial partnership.

That concept is most closely tied to Mars Ice Mapper, a mission still in early development that will fly a radar mapping payload to look for subsurface ice deposits to support future robotic or human missions. That communications network, NASA officials said, would increase the amount of data that mission could return by a factor of 100.

Both Mars Ice Mapper and the proposed communications network will not launch until later in the decade, if approved. Ianson said a decision on changing MRO’s orbit to support Mars 2020 will be made “in the coming months.”

Critical engine test for NASA's Space Launch System megarocket shuts down earlier than planned

 The SLS core booster will help launch NASA's Artemis 1 mission to the moon.

NASA fired up the core stage of its massive new rocket — the Space Launch System (SLS) — on Saturday (Jan. 16) in a critical test that ended prematurely when the booster's engines shut down earlier than planned. 

Smoke and flames billowed from the four RS-25 engines that power the behemoth rocket's core booster, a centerpiece of NASA's Artemis moon program, as it roared to life atop a test stand at NASA's Stennis Space Center near Bay St. Louis, Mississippi. Ignition occurred at 5:27  

EST (2227 GMT), with 700,000 gallons (2.6 million liters) of cryogenic fuel flowing through the engines as they roared for just over 1 minute, much shorter than planned. 

The test was supposed to run for 485 seconds (or just over 8 minutes), which is the amount of time the engines will burn during flight. Following engine ignition, the four RS-25 engines fired for just over 60 seconds, NASA said.

"Not everything went according to script today," NASA chief Jim Bridenstine said late Saturday after the test. "But we got a lot of great data, a lot of great information."

An early engine shutdown 

It's still too early to know exactly what caused the early shutdown in Saturday's engine test. 

Flight controllers could be heard during the test referring to an "MCF" (a major component failure) apparently related to engine No. 4 on the SLS booster. John Honeycutt, NASA's SLS program manager, added that at about the 60-second mark, cameras caught a flash in a protective thermal blanket on the engine, though its cause and significance remain to be determined.

Honeycutt said it's too early to know if a second hot-fire test will be required at Stennis, or if it can be done later at NASA's Kennedy Space Center in Florida, where the SLS is scheduled to launch the uncrewed Artemis 1 mission around the moon by the end of this year. Similarly, it's too early to know if Artemis 1 will still be able to launch this year.

"I think it's still too early to tell," Bridenstine said of whether a 2021 launch for Artemis 1 is still in the cards. "As we figure out what went wrong, we're going to know kind of what the future holds."

During a press conference on Tuesday (Jan. 12), John Shannon vice president and program manager for SLS at Boeing, said that the engines needed to run for a certain amount of time to get the data they needed. "If we had an early shutdown, for whatever reason, we get all of the engineering data we need to have high confidence in the vehicle at about 250 seconds," Shannon said. 

Since the test was stopped short of 250 seconds, and before the teams were able to gimble (or move) the engines, exactly how much data and how confident the teams are in the vehicle is yet to be determined. 

Saturday's test was initially moved up an hour to 4 p.m. EST (1900 GMT) as test preparations were ahead of schedule. However, during the countdown, engineers put the count on hold to work through water deflection system checks and other tests on the engine test stand. The teams were able to work through the issues and resume the count in time to complete the test Saturday, despite the short run time.

The exercise, known as a hot-fire test, put the core Space Launch System booster components — the four RS-25 main engines, fuel tanks and the rockets computers and avionics — through their paces. The test simulated a launch while holding the rocket firmly in place, affixed to a test stand. (The same test stand was used to test out the engines on both NASA's Saturn V rocket and space shuttle orbiters.) 

"The SLS rocket is the most powerful rocket ever built in the history of humanity," Bridenstine said on NASA TV shortly before the test. "This is the same rocket that, by the end of this year, will be launching an Orion crew capsule around the moon."

Anatomy of the Space Launch System

NASA's Space Launch System was first conceived in 2011 and is finally coming together for an uncrewed trip around the moon sometime later this year. 

Each SLS rocket will use four RS-25 rocket engines to launch its 212-foot (65-meter) core stage. The rocket will also rely on two solid rocket boosters and an upper stage to launch NASA's Orion crew capsule beyond low-Earth orbit.

Together, SLS and Orion are the two major components of NASA's Artemis moon program which seeks to return astronauts to the moon as soon as 2024.

The agency currently has 16 RS-25 engines on hand, which were salvaged from the agency's now-retired space shuttle program. Those engines will be used on the first four SLS rocket launches for Artemis missions 1 through 4. (Those flights include the program's first crewed moon landing, Artemis 3, and a follow-up flight.)

Since the engines on those first missions are shuttle leftovers, they've been overhauled with new computer controllers as well as upgrades that ensure they can handle the higher performance demands of an SLS launch, NASA officials have said.

That's not the only part recycled from programs past. Like the engines, the solid rocket boosters were also used to propel NASA's fleet of space shuttles to orbit. They too, have been modified to work with SLS. But they won't be used forever. As technology evolves, the side boosters will be swapped out for advanced boosters. 

The SLS will contain a pair of these boosters strapped onto the side of the core stage. It consists of four RS-25 engines at the base of the vehicle, and stacked on top will be the rocket’s components with an Orion capsule and service module perched atop. 

The whole vehicle will be capped off with a launch orbit system that is designed to pull the capsule away from the rocket if something goes wrong during a launch.

Gravitational Wave Search Finds Tantalizing New Clue.

 

    This illustration shows the NANOGrav project observing cosmic objects called pulsars in 

    an effort  detect gravitational waves – ripples in the fabric of space. The project is seeking a 

    low- level gravitational wave background signal that is thought to be present throughout 

    the universe.  Credit: NANOGrav/T. Klein

An international team of scientists may be close to detecting faint ripples in space-time that fill the universe.

Pairs of black holes billions of times more massive than the Sun may be circling one another, generating ripples in space itself. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has spent more than a decade using ground-based radio telescopes to look for evidence of these space-time ripples created by behemoth black holes. This week, the project announced the detection of a signal that may be attributable to gravitational waves, though members aren't quite ready to claim success.

Gravitational waves were first theorized by Albert Einstein in 1916, but they weren't directly detected until nearly a century later. Einstein showed that rather than being a rigid backdrop for the universe, space is a flexible fabric that is warped and curved by massive objects and inextricably linked with time. In 2015, a collaboration between the U.S.-based Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer in Europe announced the first direct detection of gravitational waves: They were emanating from two black holes - each with a mass about 30 times greater than the Sun - circling one another and merging.

In a new paper published in the January 2021 issue of the Astrophysical Journal Supplements, the NANOGrav project reports the detection of unexplained fluctuations, consistent with the effects of gravitational waves, in the timing of 45 pulsars spread across the sky and measured over a span of 12 1/2 years.

Pulsars are dense nuggets of material left over after a star explodes as a supernova. As seen from Earth, pulsars appear to blink on and off. In reality, the light comes from two steady beams emanating from opposite sides of the pulsar as it spins, like a lighthouse. If gravitational waves pass between a pulsar and Earth, the subtle stretching and squeezing of space-time would appear to introduce a small deviation in the pulsar's otherwise regular timing. But this effect is subtle, and more than a dozen other factors are known to influence pulsar timing as well. A major part of the work done by NANOGrav is to subtract those factors from the timing data for each pulsar before looking for signs of gravitational waves.

LIGO and Virgo detect gravitational waves from individual pairs of black holes (or other dense objects called neutron stars). By contrast, NANOGrav is looking for a persistent gravitational wave "background," or the noiselike combination of waves created over billions of years by countless pairs of supermassive black holes orbiting one another across the universe. These objects produce gravitational waves with much longer wave lengths than those detected by LIGO and Virgo - so long that it might take years for a single wave to pass by a stationary detector. So while LIGO and Virgo can detect thousands of waves per second, NANOGrav's quest requires years of data.

As tantalizing as the latest finding is, the NANOGrav team isn't ready to claim they've found evidence of a gravitational wave background. Why the hesitation? In order to confirm direct detection of a signature from gravitational waves, NANOGrav's researchers will have to find a distinctive pattern in the signals between individual pulsars. According to Einstein's theory of general relativity, the effect of the gravitational wave background should influence the timing of the pulsars slightly differently based on their positions relative to one another.

At this point, the signal is too weak for such a pattern to be distinguishable. Boosting the signal will require NANOGrav to expand its dataset to include more pulsars studied for even longer lengths of time, which will increase the array's sensitivity. NANOGrav is also pooling its data with those from other pulsar timing array experiments in a joint effort by the International Pulsar Timing Array, a collaboration of researchers using the world's largest radio telescopes.

"Trying to detect gravitational waves with a pulsar timing array requires patience," said Scott Ransom with the National Radio Astronomy Observatory and the current chairperson of NANOGrav. "We're currently analyzing over a dozen years of data, but a definitive detection will likely take a couple more. It's great that these new results are exactly what we would expect to see as we creep closer to a detection."

The NANOGrav team discussed their findings at a press conference on Jan. 11 at the 237th meeting of the American Astronomical Society, held virtually from Jan. 10 to 15. Michele Vallisneri and Joseph Lazio, both astrophysicists at NASA's Jet Propulsion Laboratory in Southern California, and Zaven Arzoumanian at NASA's Goddard Space Flight Center in Maryland are co-authors of the paper. Joseph Simon, a researcher at University of Colorado Boulder and the paper's lead author, conducted much of the analysis for the paper as a postdoctoral researcher at JPL. Multiple NASA postdoctoral fellows have participated in the NANOGrav research while at JPL. NANOGrav is a collaboration of U.S. and Canadian astrophysicists. The data in the new study was collected using the Green Bank antenna in West Virginia and the Arecibo dish in Puerto Rico before its recent collapse.