1. NASA’s OSIRIS-REx Mission Will Have a Map for That

    May 25, 2016 -

    On Sept. 8, NASA’s OSIRIS-REx spacecraft is scheduled to launch for terra incognita: the unknown surface of the near-Earth asteroid Bennu. Like expeditions of old, OSIRIS-REx’s mission includes mapping the exotic terrain it explores.

    Bennu is part of the debris left over from the formation of the solar system and is pristine enough to hold clues to that very early history. OSIRIS-REx – which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer – will study Bennu in detail and collect a sample to send to Earth for in-depth analysis. The mission also will investigate how pressure from sunlight influences the path of this traveling asteroid.

    “I like to say the first thing any explorer does upon reaching a new land is to start making maps,” said Ed Beshore, deputy principal investigator of OSIRIS-REx at the University of Arizona in Tucson.

    The mapping of the near-Earth asteroid Bennu is one of the science goals of NASA’s OSIRIS-REx mission, and an integral part of spacecraft operations. The spacecraft will spend a year surveying Bennu before collecting a sample that will be returned to Earth for analysis. Credits: NASA/Goddard/University of Arizona

    The mapping of the near-Earth asteroid Bennu is one of the science goals of NASA’s OSIRIS-REx mission, and an integral part of spacecraft operations. The spacecraft will spend a year surveying Bennu before collecting a sample that will be returned to Earth for analysis.
    Credits: NASA/Goddard/University of Arizona

    For OSIRIS-REx, mapping is mission-critical. It’s one of the primary science goals and an integral part of spacecraft operations. The spacecraft will spend a year flying in close proximity to Bennu – its five instruments imaging the asteroid, documenting its lumpy shape, and surveying its chemical and physical properties.

     

    This information will be used to produce four top-level maps for identifying the site where sample will be collected. These maps will indicate which sites are scientifically most valuable, where the spacecraft can touch the asteroid safely, where navigation can deliver the spacecraft, and where there is enough loose rock that can be collected.

    About a dozen potential sampling sites will be chosen to start. Once this list has been winnowed down, reconnaissance maps will provide detailed views of the few remaining candidates. Later, after the sampling is done, the team will refine some maps to provide context for laboratory analysis of the material and to aid future studies of asteroids.

    “Each map will pull together different kinds of data to answer an independent question,” said Lucy Lim, OSIRIS-REx assistant project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

    One top-level map will deal with the safety of the spacecraft. The team has to make sure OSIRIS-REx won’t encounter hazards as it approaches Bennu and executes its touch-and-go – or TAG – maneuver. A mechanical arm that functions like a pogo stick will be extended from the spacecraft. The spacecraft will slowly approach the asteroid until the sample head at the end of the arm “kisses” the surface. Then, OSIRIS-REx will move away from the asteroid.

    The target area for TAG will be a circle that measures 164 feet (50 meters) across.

    “We have to be able to say with a high degree of confidence that the spacecraft will be safe if it touches the surface anywhere within that circle,” said David Lorenz, OSIRIS-REx TAG lead at Goddard.

    To determine that, the team will look at the tilt of the landscape, temperature readings, and whether plumes of material are coming off the asteroid. Another consideration will be the amount of light reflected by the surface. That’s important because OSIRIS-REx will bounce laser signals off the surface. If an area is too dark, there won’t be enough return signal; an area that’s too bright will blind the detector.

    Hazards such as large boulders and steep cliffs will be identified at a different stage.

    Another top-level map will address the ability to deliver OSIRIS-REx to its target. This is primarily a navigation question: Can the spacecraft be brought to a target site at the correct speed? (Both vertical speed and sideways speed matter.) If not, the spacecraft will be in danger of crashing or tipping over in a so-called stubbed-toe scenario.

    Bennu’s mass makes navigating a particular challenge. The asteroid will be one of the smallest objects ever visited by a planetary spacecraft. Bennu has very little gravity – so little that pressure from sunlight on OSIRIS-REx will almost equal the force of Bennu’s gravity. To stay in orbit, the spacecraft will have to remain within a mile and a half (about 2.4 kilometers) of Bennu. Any farther than that, and the pressure from sunlight will push it away from the asteroid.

    “The bottom line is that we’re paying a lot more attention to modeling very small accelerations, such as those exerted by solar radiation pressure, than previous missions have had to do,” said Michael Moreau, OSIRIS-REx flight dynamics system manager at Goddard.

    The third of these maps will determine where the right kind of surface material is located. The sample head, which looks like a big automotive air filter, can take in dirt, dust and bits of gravel measuring less than three-fourths of an inch (2 centimeters). At least 2 ounces (60 grams) of material needs to be collected, but the sample head can hold up to 4.4 pounds (2 kilograms).

    “Our goal is to maximize the amount of sample for OSIRIS-REx,” said Kevin Walsh, an OSIRIS-REx co-investigator at the Southwest Research Institute in Boulder, Colorado. “We have tested the sample head in the lab and know how it performs, and we will hunt for the right sort of environment on Bennu.”

    To find that, the team will look at images, tilt measurements and thermal information, which reveals how the material on the surface stores and releases heat. Coarser, rockier grains will absorb more heat from the sun and give it off slowly during the asteroid’s night. Fine-grained particles will lose heat very quickly once they are out of the sunlight.

    The fourth top-level map will evaluate the scientific value of the surface on Bennu. From remote observations, the team assumes that Bennu should contain water and organic – or carbon-rich – material, but they don’t know yet how this material is distributed across the surface.

    “Some of the most interesting sites will be those that offer fresh material – perhaps exposed by an impact, a crack or plume activity like comets have – and those with diverse material,” said Keiko Nakamura-Messenger, OSIRIS-REx sample site scientist and the deputy lead for curation at NASA’s Johnson Space Center in Houston. “We also believe the coldest place has higher science value, because that is where organics are likely to be better preserved.”

    To figure this out, the team will look at geological features, mineralogy, chemical composition and temperature.

    All of these maps will be built on a 3-D shape model of Bennu. The team is already using a preliminary shape model, produced from radar observations of the asteroid. But a new shape model with much higher resolution will be made once OSIRIS-REx surveys Bennu.

    “The shape model is the framework – the one piece every map needs to have,” said Eric Palmer, an OSIRIS-REx collaborator at the Planetary Science Institute in Tucson. “It also provides a way of correcting scientific observations so that you can make apples-to-apples comparisons.”

    The team has two ways of deriving the detailed shape of Bennu. One is to make precise measurements of the round-trip distance from the spacecraft to the asteroid using the on-board laser altimeter. The other is the so-called shape-by-shading technique – or stereophotoclinometry – which deduces the 3-D lay of the land from multiple images taken from different angles under a range of lighting conditions.

    Beshore pointed out one more reason to put all this effort into mapping. “These maps of Bennu are going to be beautiful,” he said.

    NASA Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering and safety and mission assurance for OSIRIS-REx. Dante Lauretta is the mission’s principal investigator at the University of Arizona, Tucson. Lockheed Martin Space Systems in Denver is building the spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA Marshall Space Flight Center in Huntsville, Alabama, manages New Frontiers for the agency’s Science Mission Directorate in Washington.

    Launch management is the responsibility of NASA’s Launch Services Program at the Kennedy Space Center in Florida.

  2. PI BLOG: The Journey to Kennedy Space Center

    May 24, 2016 -

    The OSIRIS-REx project continues to progress seamlessly through the Assembly, Test, and Launch Operations (ATLO) phase. We are now done with the AT portion of this phase and have started LO. The test phase ended with the completion of the last major environmental test: the thermal vacuum test. With the test program complete, the team made the transition to the launch site at Kennedy Space Center […]

  3. NASA Begins Launch Preparations for the First U.S. Asteroid Sampling Mission

    May 23, 2016 -

    NASA’s first spacecraft designed to return a piece of an asteroid to Earth arrived Friday, May 20, at the agency’s Kennedy Space Center in Florida, and has begun final preparations in advance of its September launch.

    The OSIRIS-REx spacecraft is unloaded from a US Air Force -17 at NASA's Kennedy Space Center Shuttle Landing Facility. Credit: University of Arizona/Erin Morton

    The OSIRIS-REx spacecraft is unloaded from a US Air Force C-17 at NASA’s Kennedy Space Center Shuttle Landing Facility. Credit: University of Arizona/Erin Morton

    The Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer (OSIRIS-REx) spacecraft will undergo final testing and fueling prior to being moved to its launch pad. The mission has a 34-day launch period beginning on Sept. 8.

    After launch, the OSIRIS-REx spacecraft will travel to the near-Earth asteroid Bennu and retrieve at least 60 grams (2.1 ounces) of pristine surface material and return it to Earth for study. Scientists expect that Bennu may hold clues to the origin of the solar system and the source of the water and organic molecules that may have made their way to Earth.

    “I’m extremely proud of our team and excited to be shipping the OSIRIS-REx spacecraft to Kennedy Space Center, said Mike Donnelly, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We still have a few major milestones to go, but I’m confident that we’ll get them done and be ready to launch on time and begin our mission to Bennu.”

    Over the weekend, the team transferred the spacecraft from the shipping container into a cleanroom and performed post-ship inspections to confirm that OSIRIS-REx arrived in good condition. The spacecraft is ready to begin its final round of testing and pre-launch checks, which are scheduled to commence later today when it will be installed onto a spin balance fixture. Further checks prior to launch will include software tests, instrument and power functional tests, spacecraft self-tests and deployments of the spacecraft’s solar panels.

    The spacecraft was transported from Buckley Air Force Base in Aurora, Colorado, on Friday aboard a U.S. Air Force C-17 cargo plane. Lockheed Martin Space Systems designed and built the spacecraft in its Littleton, Colorado, facility.“Delivering OSIRIS-REx to the launch site marks an important milestone, one that’s been many years in the making,” said Rich Kuhns, OSIRIS-REx program manager at Lockheed Martin Space Systems Company. “The spacecraft has undergone a rigorous environmental test

    After arriving at NASA's Kennedy Space Center, the OSIRIS-REx spacecraft sits on a launch vehicle adapter ring in the Payload Hazardous Servicing Facility. Credit: University of Arizona/Erin Morton

    After arriving at NASA’s Kennedy Space Center, the OSIRIS-REx spacecraft sits on a launch vehicle adapter ring in the Payload Hazardous Servicing Facility. Credit: University of Arizona/Erin Morton

    program in Denver, but we still have plenty of work ahead of us. Many on our team have temporarily moved to Florida so they can continue final processing and have the spacecraft ready for the Sept. 8 launch date.”

    After launch, the OSIRIS-REx spacecraft has an approximately two-year cruise to reach Bennu in 2018. Upon arrival, OSIRIS-REx will spend two years conducting surface mapping and sample site reconnaissance operations before performing the sampling maneuver in 2020. OSIRIS-REx will then deliver the pristine sample of Bennu back to Earth in 2023.

    “This team has done a phenomenal job of assembling and testing the spacecraft,” said Dante Lauretta, principal investigator for OSIRIS-REx at the University of Arizona, Tucson. “As we begin the final preparations for launch, I am confident that this spacecraft is ready to perform its science operations at Bennu.  And I can’t wait to fly it.”

    NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx.  Dante Lauretta is the mission’s principal investigator at the University of Arizona.  Lockheed Martin Space Systems in Denver built the spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages NASA’s New Frontiers Program for the agency’s Science Mission Directorate in Washington. Launch and countdown management is the responsibility of NASA’s John F. Kennedy Space Center in Florida.

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