1. NASA’s Newly Arrived OSIRIS-REx Spacecraft Already Discovers Water on Asteroid

    December 10, 2018 -

    Recently analyzed data from NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission has revealed water locked inside the clays that make up its scientific target, the asteroid Bennu.

    This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec. 2 by the OSIRIS-REx spacecraft from a range of 15 miles (24 km).
    Credit: NASA/Goddard/University of Arizona

    During the mission’s approach phase, between mid-August and early December, the spacecraft traveled 1.4 million miles (2.2 million km) on its journey from Earth to arrive at a location 12 miles (19 km) from Bennu on Dec. 3. During this time, the science team on Earth aimed three of the spacecraft’s instruments towards Bennu and began making the mission’s first scientific observations of the asteroid. OSIRIS-REx is NASA’s first asteroid sample return mission.

    Data obtained from the spacecraft’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES), reveal the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as “hydroxyls.” The team suspects that these hydroxyl groups exist globally across the asteroid in water-bearing clay minerals, meaning that at some point, Bennu’s rocky material interacted with water. While Bennu itself is too small to have ever hosted liquid water, the finding does indicate that liquid water was present at some time on Bennu’s parent body, a much larger asteroid.

    “The presence of hydrated minerals across the asteroid confirms that Bennu, a remnant from early in the formation of the solar system, is an excellent specimen for the OSIRIS-REx mission to study the composition of primitive volatiles and organics,” said Amy Simon, OVIRS deputy instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “When samples of this material are returned by the mission to Earth in 2023, scientists will receive a treasure trove of new information about the history and evolution of our solar system.”

    Additionally, data obtained from the OSIRIS-REx Camera Suite (OCAMS) corroborate ground-based telescopic observations of Bennu and confirm the original model developed in 2013 by OSIRIS-REx Science Team Chief Michael Nolan and collaborators. That model closely predicted the asteroid’s actual shape, with Bennu’s diameter, rotation rate, inclination, and overall shape presented almost exactly as projected.

    This preliminary shape model of asteroid Bennu was created from a compilation of images taken by OSIRIS-REx’s PolyCam camera during the spacecraft’s approach toward Bennu during the month of November. This 3D shape model shows features on Bennu as small as six meters.
    Credit: NASA/Goddard/University of Arizona

    One outlier from the predicted shape model is the size of the large boulder near Bennu’s south pole. The ground-based shape model calculated this boulder to be at least 33 feet (10 meters) in height. Preliminary calculations from OCAMS observations show that the boulder is closer to 164 feet (50 meters) in height, with a width of approximately 180 feet (55 meters).

    Bennu’s surface material is a mix of very rocky, boulder-filled regions and a few relatively smooth regions that lack boulders. However, the quantity of boulders on the surface is higher than expected. The team will make further observations at closer ranges to more accurately assess where a sample can be taken on Bennu to later be returned to Earth.

    “Our initial data show that the team picked the right asteroid as the target of the OSIRIS-REx mission. We have not discovered any insurmountable issues at Bennu so far,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “The spacecraft is healthy and the science instruments are working better than required. It is time now for our adventure to begin.”

    The mission currently is performing a preliminary survey of the asteroid, flying the spacecraft in passes over Bennu’s north pole, equator, and south pole at ranges as close as 4.4 miles (7 km) to better determine the asteroid’s mass. The mission’s scientists and engineers must know the mass of the asteroid in order to design the spacecraft’s insertion into orbit because mass affects the asteroid’s gravitational pull on the spacecraft. Knowing Bennu’s mass will also help the science team understand the asteroid’s structure and composition.

    This survey also provides the first opportunity for the OSIRIS-REx Laser Altimeter (OLA), an instrument contributed by the Canadian Space Agency, to make observations, now that the spacecraft is in proximity to Bennu.

    The spacecraft’s first orbital insertion is scheduled for Dec. 31, and OSIRIS-REx will remain in orbit until mid-February 2019, when it exits to initiate another series of flybys for the next survey phase. During the first orbital phase, the spacecraft will orbit the asteroid at a range of 0.9 miles (1.4 km) to 1.24 miles (2.0 km) from the center of Bennu — setting new records for the smallest body ever orbited by a spacecraft and the closest orbit of a planetary body by any spacecraft.

    Goddard provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space Systems in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for the Science Mission Directorate in Washington.

  2. NASA’S OSIRIS-REx Spacecraft Arrives at Asteroid Bennu

    December 3, 2018 -

    NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft completed its 1.2 billion-mile (2 billion-kilometer) journey to arrive at the asteroid Bennu Monday. The spacecraft executed a maneuver that transitioned it from flying toward Bennu to operating around the asteroid.

    This series of images taken by the OSIRIS-REx spacecraft shows Bennu in one full rotation from a distance of around 50 miles (80 km). The spacecraft’s PolyCam camera obtained the 36 2.2-millisecond frames over a period of four hours and 18 minutes. Credit: NASA/Goddard/University of Arizona

    Now, at about 11.8 miles (19 kilometers) from Bennu’s Sun-facing surface, OSIRIS-REx will begin a preliminary survey of the asteroid. The spacecraft will commence flyovers of Bennu’s north pole, equatorial region, and south pole, getting as close as nearly 4 miles (7 kilometers) above Bennu during each flyover.

    The primary science goals of this survey are to refine estimates of Bennu’s mass and spin rate, and to generate a more precise model of its shape. The data will help determine potential sites for later sample collection.

    OSIRIS-REx’s mission will help scientists investigate how planets formed and how life began, as well as improve our understanding of asteroids that could impact Earth. Asteroids are remnants of the building blocks that formed the planets and enabled life. Those like Bennu contain natural resources, such as water, organics and metals. Future space exploration and economic development may rely on asteroids for these materials.

    “As explorers, we at NASA have never shied away from the most extreme challenges in the solar system in our quest for knowledge,” said Lori Glaze, acting director for NASA’s Planetary Science Division. “Now we’re at it again, working with our partners in the U.S. and Canada to accomplish the Herculean task of bringing back to Earth a piece of the early solar system.”

    The mission’s navigation team will use the preliminary survey of Bennu to practice the delicate task of navigating around the asteroid. The spacecraft will enter orbit around Bennu on Dec. 31 –thus making Bennu, which is only about 1,600 feet (492 meters) across — or about the length of five football fields — the smallest object ever orbited by a spacecraft. It’s a critical step in OSIRIS-REx’s years-long quest to collect and eventually deliver at least two ounces (60 grams) of regolith — dirt and rocks — from Bennu to Earth.

    Starting in October, OSIRIS-REx performed a series of braking maneuvers to slow the spacecraft down as it approached Bennu. These maneuvers also targeted a trajectory to set up Monday’s maneuver, which initiates the first north pole flyover and marks the spacecraft’s arrival at Bennu.

    “The OSIRIS-REx team is proud to cross another major milestone off our list — asteroid arrival,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “Initial data from the approach phase show this object to have exceptional scientific value. We can’t wait to start our exploration of Bennu in earnest. We’ve been preparing for this moment for years, and we’re ready.”

    OSIRIS-REx mission marks many firsts in space exploration. It will be the first U.S. mission to carry samples from an asteroid back to Earth and the largest sample returned from space since the Apollo era. It’s the first to study a primitive B-type asteroid, which is an asteroid that’s rich in carbon and organic molecules that make up life on Earth. It is also the first mission to study a potentially hazardous asteroid and try to determine the factors that alter their courses to bring them close to Earth.

    “During our approach toward Bennu, we have taken observations at much higher resolution than were available from Earth,” said Rich Burns, the project manager of OSIRIS-REx at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “These observations have revealed an asteroid that is both consistent with our expectations from ground-based measurements and an exceptionally interesting small world. Now we embark on gaining experience flying our spacecraft about such a small body.”

    When OSIRIS-REx begins to orbit Bennu at the end of this month, it will come close to approximately three quarters of a mile (1.25 kilometers) to its surface. In February 2019, the spacecraft begins efforts to globally map Bennu to determine the best site for sample collection. After the collection site is selected, the spacecraft will briefly touch the surface of Bennu to retrieve a sample. OSIRIS-REx is scheduled to return the sample to Earth in September 2023.

    Goddard provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama for the agency’s Science Mission Directorate in Washington.

  3. TAGSAM Testing Complete: OSIRIS-REx Prepared to TAG an Asteroid

    By Christine Hoekenga

    November 16, 2018 -

    On Nov. 14, NASA’s OSIRIS-REx spacecraft stretched out its robotic sampling arm for the first time in space. The arm, more formally known as the Touch-and-Go Sample Acquisition Mechanism (TAGSAM), is key to the spacecraft achieving the primary goal of the mission: returning a sample from asteroid Bennu in 2023.

    OSIRIS-REx's TAGSAM Head as Imaged by SamCam

    This image, showing the OSIRIS-REx Touch-and-Go Sample Acquisition Mechanism (TAGSAM) sampling head extended from the spacecraft at the end of the TAGSAM arm, was taken by the SamCam camera on Nov. 14, 2018 during a visual checkout of the spacecraft’s sampling system. A similar observation will be taken after TAG to help document the asteroid material collected in the TAGSAM head. Credit: NASA/Goddard/University of Arizona

    As planned, engineers at Lockheed Martin commanded the spacecraft to move the arm through its full range of motion – flexing its shoulder, elbow, and wrist “joints.” This long-awaited stretch, which was confirmed by telemetry data and imagery captured by the spacecraft’s SamCam camera, demonstrates that the TAGSAM head is ready to collect a sample of loose dirt and rock (called regolith) from Bennu’s surface.

    “The TAGSAM exercise is an important milestone, as the prime objective of the OSIRIS-REx mission is to return a sample of Bennu to Earth,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “This successful test shows that, when the time comes, TAGSAM is ready to reach out and tag the asteroid.”

    Years of innovation

    Lockheed Martin engineers spent more than a decade designing, building, and testing TAGSAM, which includes an 11-foot (3.35-meter) arm with three articulating joints, a round sampler head at the end of the arm that resembles the air filter in a car, and three bottles of high-pressure nitrogen gas.

    This test deployment was a rehearsal for a date in mid-2020 when the spacecraft will unfold the TAGSAM arm again, slowly descend to Bennu’s surface, and briefly touch the asteroid with the sampler head. A burst of nitrogen gas will stir up regolith on the asteroid’s surface, which will be caught in the TAGSAM head. The TAG sequence will take about five seconds, after which the spacecraft will execute small maneuvers to carefully back away from Bennu. Afterward, SamCam will image the sampler head, as it did during the test deployment, to help confirm that TAGSAM collected at least 2.1 ounces (60 grams) of regolith.

    The TAGSAM mechanism was designed for the key challenge unique to the OSIRIS-REx mission: collecting a sample from the smallest planetary body ever to be orbited by a spacecraft. “First-of-its-kind innovations like this one serve as the precursor for future missions to small bodies,” said Sandy Freund, systems engineer manager and Lockheed Martin OSIRIS-REx MSA manager. “By proving out these technologies and techniques, we are going to be able to return the largest sample from space in half a century and pave the way for other missions.”

    A month of testing

    The unfolding of the TAGSAM arm was the latest and most significant step in a series of tests and check-outs of the spacecraft’s sampling system, which began in October when OSIRIS-REx jettisoned the cover that protected the TAGSAM head during launch and the mission’s outbound cruise phase. Shortly before the cover ejection, and again the day after, OSIRIS-REx performed two spins called Sample Mass Measurements. By comparing the spacecraft’s inertial properties during these before-and-after spins, the team confirmed that the 2.67-pound (1.21-kilogram) cover was successfully ejected on Oct. 17.

    A week later, on Oct. 25, the Frangibolts holding the TAGSAM arm in place fired successfully, releasing the arm and allowing the team to move it into a parked position just outside its protective housing. After resting in this position for a few weeks, the arm was fully deployed into its sampling position, its joints were tested, and images were captured with SamCam. The spacecraft will execute two additional Sample Mass Measurements over the next two days. The mission team will use these spins as a baseline to compare with the results of similar spins that will be conducted after TAG in 2020 in order to confirm the mass of the sample collected.

    Although the sampling system was rigorously tested on Earth, this rehearsal marked the first time that the team has deployed TAGSAM in the micro-gravity environment of space.

    “The team is very pleased that TAGSAM has been released, deployed, and is operating as commanded through its full range of motion.” said Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It has been restrained for over two years since launch, so it is gratifying to see it out of its shackles and performing well.”

    OSIRIS-REx is scheduled to arrive at Bennu on Dec. 3. It will spend nearly one year surveying the asteroid with five scientific instruments so that the mission team can select a location that is safe and scientifically interesting to collect the sample.

    “Now that we have put TAGSAM through its paces in space and know it is ready to perform at Bennu, we can focus on the challenges of navigating around the asteroid and seeking out the best possible sample site,” said Lauretta.

  4. NASA’s OSIRIS-REx Executes Fourth Asteroid Approach Maneuver

    November 13, 2018 -

    Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its Attitude Control System (ACS) thrusters.

    NASA’s OSIRIS-REx spacecraft executed its fourth Asteroid Approach Maneuver (AAM-4) yesterday. The spacecraft fired its Attitude Control System (ACS) thrusters to slow the spacecraft from approximately 0.31 mph (0.14 m/sec) to 0.10 mph (0.04 m/sec). The ACS thrusters are capable of velocity changes as small as 0.02 mph (0.01 m/sec). The mission team will continue to examine telemetry and tracking data over the next week to verify the new trajectory. The maneuver targeted the spacecraft to fly through a corridor designed for the collection of high-resolution images that will be used to build a shape model of Bennu.

    With the execution of AAM-4, the OSIRIS-REx spacecraft concludes a six-week series of Bennu approach maneuvers. AAM-1 and AAM-2, which executed on Oct. 1 and Oct. 15 respectively, slowed the spacecraft by a total of approximately 1,088 mph (486 m/sec). AAM-3 and AAM-3A, which executed on Oct. 29 and Nov. 5 respectively, further refined the spacecraft’s trajectory and speed to set the conditions for a successful AAM-4 maneuver. After a final correction maneuver scheduled for Nov. 30, the spacecraft will be on track to arrive at a position 12 miles (20 km) from Bennu on Dec. 3.

  5. Behind the Scenes of REXIS: Uncovering an Instrument in Flight

    By Rebecca Masterson, REXIS Instrument Program Manager

    November 13, 2018 -

    On Sept. 14, OSIRIS-REx’s REXIS instrument opened its radiation cover, as scheduled, after two years in space. The cover had been in place to protect REXIS’s charge-coupled devices (CCDs) from degradation due to radiation exposure during the spacecraft’s cruise to Bennu. The REXIS student team designed and built the cover with input from MIT and NASA Goddard mentors and members of the OSIRIS-REx review board.

    Figure 1: CAD model of the REXIS cover in the closed position, showing the Frangibolt housing and cover heater. The flight instrument also includes a heater on the Frangibolt housing that is not shown here.

    Since its installation, the radiation cover had been held closed with a titanium bolt that was threaded through a TiNi Aerospace FD04 Frangibolt and a switch washer (see Figure 1). When it was time to release the cover, the team sent REXIS a command to heat the Frangibolt until the shape memory alloy expanded. This put the bolt under tension, causing structural failure, so that the cover was free to swing open. The switch washer sensed the change in pre-load at the joint and sent a signal to the REXIS electronics board to cut power to the Frangibolt, stopping the activity.

    Figure 2: Photo of the REXIS flight instrument (before spacecraft integration) with radiation cover open. This configuration is the most-likely current configuration of the instrument on-board OSIRIS-REx after firing the Frangibolt.

    In the event that the switch washer did not work as expected, the team had also set a software timer to end the actuation activity in order to ensure that the Frangibolt did not overheat. The exact time needed to actuate the Frangibolt was unknown, as it depended heavily on the temperatures of the actuator and the cover as well as the pre-load in the joint. Therefore, the REXIS team tested both the flight instrument and spare covers in advance to try to set this timer correctly. Three attempts to open the instrument were planned, each with a slightly longer timer setting.

    For the first attempt, the team set the REXIS firing timer to 57 seconds. If the switch washer didn’t show actuation in that time, the bolt was programmed to turn off. The firing command was sent to the instrument at about 16:32 UTC. Fifty-five seconds later, the switch washer indicated that the Frangibolt had actuated … with only two seconds to spare. Kudos to the team that tested the spare cover over various temperature ranges in order to guide us to such a perfect timer setting.

    We also saw evidence of the firing in the onboard instrument temperature sensors: the housing temperature and the CCD temperature both decreased after the firing, which indicated that the cover was no longer conductively connected to the instrument tower (see Figure 3).

     

    Figure 3: The REXIS housekeeping temperatures before and after firing also show changes expected with the cover open. Both the CCD temperatures (top plot) and the Frangibolt housing temperature (middle plot, “Frangibolt”) decrease after the firing event indicating that the cover and its heater are no longer thermally coupled to the rest of the instrument.

     

    The duty cycle of the housing heater and the cover heater also changed as expected. The REXIS Frangibolt housing heater stayed on after the cover opening  since the housing is no longer getting heat from the cover heater. The cover heater duty cycle has also lengthened since the thermal mass has decreased (see Figure 4).

     

    Figure 4: REXIS cover heater current values during the cover opening event. Before the cover was open both the housing heater and the cover heater were cycling with a short duty cycle. The changes in the data after the firing attempt indicate that the housing heater is now always on and the cover heater is cycling less frequently. This behavior is expected in the cover open state.

     

    REXIS took 30 minutes of science data before and after the Frangibolt firing so we could compare the spectra. With the cover open, we were expecting to see an increase in the rate of events detected by the CCDs, dominantly in the low energy portion of the x-ray spectrum due to the Cosmic X-ray Background (CXB). The cover included an Fe-55 calibration source that shone on the CCDs and had been used to monitor the instrument status for its two years in flight. Opening the cover removed that source from the field of view of the CCDs, so we also expected to see a decrease in the Fe-55 energy detected. As expected, the rate of events detected by the CCDs increased, as shown in Figure 4. The x-ray spectrum from one of the instrument’s highest performing CCD nodes is shown in Figure 5.

    Figure 5: Rate of X-ray events detected by the CCDs during the cover opening activity. The detected event rate has a discontinuous step in the 30 minutes before and after the cover opened. The increase in the event rate is due to diffuse x-ray emission of the cosmic x-ray background as expected with an open cover.

    The x-ray spectrum measured in the low energy range increased, just as expected for the CXB ,while the calibration source signal from Fe-55 became less pronounced. The data in Figure 5 and Figure 6 are consistent with a fully open REXIS cover.

    Figure 6: The x-ray spectrum is a measure of the number of events detected by the CCDs as a function of energy. The red line is the x-ray spectra detected by one of the highest-performing nodes in the REXIS detector array before the cover opened. There is a peak 5.9 keV (the blue shaded region) from the cover-mounted internal Fe-55 x-ray calibration source. The low energy spectrum is due to only internal noise. The spectrum after the cover opened for the same node (black line) shows detection of a low-energy continuum consistent with predictions of the cosmic x-ray background (blue dashed line) and a weakening of the Fe-55 line indicating that the instrument is now looking at cosmic x-rays from space instead of the underside of the cover.

    Given both this science and engineering data, we are confident that our radiation cover is open and out of the field of view of the REXIS CCDs. Now the REXIS team can start doing real external calibrations. REXIS will be looking at some Cosmic X-Ray Background (CXB) in early October and then will turn to check out the Crab Nebula in November.

  6. NASA’s OSIRIS-REx Executes Third Asteroid Approach Maneuver

    October 29, 2018 -

    Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its trajectory correction maneuver (TCM) engines.

    NASA’s OSIRIS-REx spacecraft executed its third Asteroid Approach Maneuver (AAM-3) today. The trajectory correction maneuver (TCM) thrusters fired in a series of two braking maneuvers designed to slow the spacecraft’s speed relative to Bennu from approximately 11.7 mph (5.2 m/sec) to .24 mph (.11 m/sec). Due to constraints that science instruments not be pointed too closely to the Sun, this maneuver was designed as two separate burns of approximately 5.8 mph (2.6 m/sec) each, to accomplish a net change in velocity of around 11.5 mph (5.13 m/sec). The mission team will continue to examine telemetry and tracking data over the next week to verify the new trajectory. The maneuver targeted the spacecraft to fly through a corridor designed for the collection of high-resolution images that will be used to build a shape model of Bennu.

    The OSIRIS-REx spacecraft is in the midst of a six-week series of final approach maneuvers. AAM-1 and AAM-2, which executed on Oct. 1 and Oct. 15 respectively, slowed the spacecraft by a total of approximately 1,088 mph (486 m/sec). The last of the burns, AAM-4, is scheduled for Nov. 12 and will adjust the spacecraft’s trajectory to arrive at a position 12 miles (20 km) from Bennu on Dec. 3.

  7. Safety & Science: OSIRIS-REx on the Lookout for Hazards During Approach

    By Christine Hoekenga

    October 17, 2018 -

    An artist’s concept of OSIRIS-REx searching for dust plumes in the vicinity of asteroid Bennu. Credit: University of Arizona

    On Sept. 12, OSIRIS-REx pointed its medium-range science camera, MapCam, toward asteroid Bennu 621,000 miles (one million kilometers) in the distance. Slewing gently side to side and up and down as it captured 64 images, the spacecraft scanned the area around the asteroid in a carefully choreographed pattern. The day before, it had collected a similar mosaic of images with its long-range science camera, PolyCam.

    Over the next few days, scientists on the ground pored over the images, looking for any signs of dust in the vicinity of the asteroid, which could present a hazard to the spacecraft as it approaches. Ultimately, they determined that the coast is clear – for now.

    But OSIRIS-REx will look for natural satellites (small moons) and conduct another search for dust plumes when the spacecraft is closer to Bennu.

    No dust was detected in this MapCam image of the area around Bennu (circled in green) taken Sept. 12, 2018 during OSIRIS-REx’s first Dust Plume Search. Credit: NASA/Goddard/University of Arizona

    While comets, with their characteristic tails and comas, are known for releasing plumes of volatile materials like ice, gas, and dust, this behavior has also been observed in some asteroids. If dust had been visible in the images collected in mid-September, it would have suggested that Bennu had comet-like plume activity in the recent past, probably in the weeks or months before OSIRIS-REx conducted its first dust search.

    Although OSIRIS-REx is designed to withstand the rigors of spaceflight and the occasional collision with stray particles, flying through a dust plume would pose a risk to the spacecraft’s instruments and solar panels. If the mission team had identified plume activity in the images, they had contingency plans to execute a braking maneuver, placing the spacecraft at a safe distance so that the dust activity could be studied further.

    The existence of dust plumes would suggest that Bennu has active deposits of ice or other volatiles. Finding frozen water on the asteroid would be an exciting result for mission scientists who are in part studying Bennu to understand whether asteroids could have been the delivery mechanism for the water and organic materials needed to seed life on Earth billions of years ago. Plumes would also have implications for where OSIRIS-REx could safely collect a sample of material from Bennu’s surface in 2020 – and what types of material would likely be in that sample.

    A view of Comet 67P backlit by the Sun makes plumes coming off the comet’s surface highly visible. Credit: ESA/Rosetta/NAVCAM

    “We probably wouldn’t want to sample too near a vent for safety reasons,” says Carl Hergenrother, the OSIRIS-REx Astronomy Working Group Lead, who helped plan the hazard searches. “But it would be interesting since plumes mean that there could be subsurface volatile material nearby.”

    OSIRIS-REx’s second dust plume search, scheduled for two days in Spring 2019 when the spacecraft will be about 3.1 miles (five kilometers) from Bennu, will look for active dust plumes coming off Bennu’s surface. For those observations, the spacecraft will be positioned between the Sun and the asteroid (at a high phase angle) so that Bennu is backlit and any dust plumes are more visible. Some of the 13 mosaics that the spacecraft captures will include offset images of the asteroid so that any jets coming from the surface are easier to see against the dark backdrop of space.

    Dust isn’t the only potential hazard that OSIRIS-REx is looking out for. Later this fall, the spacecraft will use PolyCam and MapCam to search for natural satellites – any chunk of rock orbiting Bennu that is larger than 10 centimeters and bright enough to be seen (which requires an albedo of at least 0.03). While most asteroids exert a weak gravitational pull due to their relatively small sizes (Bennu has a diameter of roughly 500 meters), they are capable of holding small moons in orbit around themselves. In fact, asteroid 243 Ida, the second asteroid ever visited by a spacecraft, surprised scientists when images from the Galileo mission revealed it had a small moon, now called Dactyl.

    Asteroid Ida and its moon, Dactyl

    243 Ida is the second asteroid visited by a spacecraft (Galileo) and the first found to have its own moon. Credit: NASA/JPL

    To look for moons, two of OSIRIS-REx’s cameras will again capture a series of carefully planned mosaics covering the area around Bennu. First, PolyCam will map the asteroid’s entire Hill Sphere (the area where a satellite could theoretically exist), looking for objects that are one meter or larger. Then, as the spacecraft gets closer, MapCam will conduct a search pattern for smaller satellites (down to 10 centimeters), which could only exist in a stable orbit closer to Bennu.

    Similar to a dust plume discovery, if OSIRIS-REx were to detect a natural satellite orbiting Bennu, it would trigger a contingency plan. The spacecraft would conduct a braking burn and stop its approach to the asteroid about 40 or 50 kilometers out. The team would then take a few weeks to closely map the moon’s orbit around Bennu and decide whether any changes need to be made to the mission plan for the spacecraft to safely avoid the satellite. Later on, the team would study the moon in more depth, collecting images and other data about its color, reflectivity, shape, size, and other features.

     

    Also similar to a dust plume detection, a moon would be an interesting scientific discovery. “If we did find a satellite, mapping its orbit would allow us to refine the mass of Bennu before going into orbit around the asteroid or even doing close approaches,” says Hergenrother. “It would also tell us more about Bennu’s history.”

    While potential hazards like dust and natural satellites present navigation, safety and other challenges, they are part of the inherent adventure of exploring a never-before-visited world. Although Bennu has been thoroughly studied from Earth, the asteroid may have many surprises in store for the mission team. Careful planning and thorough observation strategies will ensure that these surprises are transformed from potential hazards into new scientific knowledge.

  8. NASA’s OSIRIS-REx Executes Second Asteroid Approach Maneuver

    October 15, 2018 -

    NASA’s OSIRIS-REx spacecraft executed its second Asteroid Approach Maneuver (AAM-2) today. The spacecraft’s main engine thrusters fired in a braking maneuver designed to slow the spacecraft’s speed relative to Bennu from 315 mph (141 m/sec) to 11.8 mph (5.2 m/sec). Likewise, the spacecraft’s approach speed dropped from nearly 7,580 miles (12,200 km) to 280 miles (450 km) per day.

    Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its main engine. Credit: University of Arizona

    The mission team will continue to examine telemetry and tracking data and will have more information over the next week. This burn marked the last planned use of the spacecraft’s main engines prior to OSIRIS-REx’s departure from Bennu in March 2021.

    The OSIRIS-REx spacecraft is in the midst of a six-week series of maneuvers designed to fly the spacecraft through a precise corridor toward Bennu. AAM-1, which executed on Oct. 1, slowed the spacecraft by 785.831 mph (351.298 m/sec) and consumed 532.4 pounds (241.5 kilograms) of fuel. AAM-3 is schedule for October 29. The last of the burns, AAM-4, is scheduled for November 12 and will adjust the spacecraft’s trajectory to arrive at a position 12 miles (20 km) from Bennu on December 3. After arrival, the spacecraft will perform a series of fly-bys over Bennu’s poles and equator.

  9. NASA’s OSIRIS-REx Executes First Asteroid Approach Maneuver

    October 1, 2018 -

    NASA’s OSIRIS-REx spacecraft executed its first Asteroid Approach Maneuver (AAM-1) today putting it on course for its scheduled arrival at the asteroid Bennu in December.

    Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its main engine. Credit: University of Arizona

    The spacecraft’s main engine thrusters fired in a braking maneuver designed to slow the spacecraft’s speed relative to Bennu from approximately 1,100 mph (491 m/sec) to 313 mph (140 m/sec). The mission team will continue to examine telemetry and tracking data as they become available and will have more information on the results of the maneuver over the next week.

    During the next six weeks, the OSIRIS-REx spacecraft will continue executing the series of asteroid approach maneuvers designed to fly the spacecraft through a precise corridor during its final slow approach to Bennu. The last of these, AAM-4, scheduled for November 12, will adjust the spacecraft’s trajectory to arrive at a position 12 miles (20 km) from Bennu on December 3. After arrival, the spacecraft will initiate asteroid proximity operations by performing a series of fly-bys over Bennu’s poles and equator.

  10. NASA’s OSIRIS-REx Begins Asteroid Operations Campaign

    August 24, 2018 -
    Asteroid Bennu moving againts a star field

    On Aug. 17, the OSIRIS-REx spacecraft obtained the first images of its target asteroid Bennu from a distance of 1.4 million miles (2.2 million km), or almost six times the distance between the Earth and Moon. This cropped set of five images was obtained by the PolyCam camera over the course of an hour for calibration purposes and in order to assist the mission’s navigation team with optical navigation efforts. Bennu is visible as a moving object against the stars in the constellation Serpens.

    After an almost two-year journey, NASA’s asteroid sampling spacecraft, OSIRIS-REx, caught its first glimpse of asteroid Bennu last week and began the final approach toward its target. Kicking off the mission’s asteroid operations campaign on Aug. 17, the spacecraft’s PolyCam camera obtained the image from a distance of 1.4 million miles (2.2 million km).

    OSIRIS-REx is NASA’s first mission to visit a near-Earth asteroid, survey the surface, collect a sample and deliver it safely back to Earth. The spacecraft has traveled approximately 1.1 billion miles (1.8 billion km) since its Sept. 8, 2016, launch and is scheduled to arrive at Bennu on Dec. 3.

    “Now that OSIRIS-REx is close enough to observe Bennu, the mission team will spend the next few months learning as much as possible about Bennu’s size, shape, surface features, and surroundings before the spacecraft arrives at the asteroid,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “After spending so long planning for this moment, I can’t wait to see what Bennu reveals to us.”

    As OSIRIS-REx approaches the asteroid, the spacecraft will use its science instruments to gather information about Bennu and prepare for arrival.  The spacecraft’s science payload comprises the OCAMS camera suite (PolyCam, MapCam, and SamCam), the OTES thermal spectrometer, the OVIRS visible and infrared spectrometer, the OLA laser altimeter, and the REXIS x-ray spectrometer.

    During the mission’s approach phase, OSIRIS-REx will:

    • regularly observe the area around the asteroid to search for dust plumes and natural satellites, and study Bennu’s light and spectral properties;
    • execute a series of four asteroid approach maneuvers, beginning on Oct. 1, slowing the spacecraft to match Bennu’s orbit around the Sun;
    • jettison the protective cover of the spacecraft’s sampling arm in mid-October and subsequently extend and image the arm for the first time in flight; and
    • use OCAMS to reveal the asteroid’s overall shape in late-October and begin detecting Bennu’s surface features in mid-November.

    After arrival at Bennu, the spacecraft will spend the first month performing flybys of Bennu’s north pole, equator, and south pole, at distances ranging between 11.8 and 4.4 miles (19 and 7 km) from the asteroid. These maneuvers will allow for the first direct measurement of Bennu’s mass as well as close-up observations of the surface. These trajectories will also provide the mission’s navigation team with experience navigating near the asteroid.

    “Bennu’s low gravity provides a unique challenge for the mission,” said Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “At roughly 0.3 miles [500 meters] in diameter, Bennu will be the smallest object that any spacecraft has ever orbited.”

    The spacecraft will extensively survey the asteroid before the mission team identifies two possible sample sites. Close examination of these sites will allow the team to pick one for sample collection, scheduled for early July 2020. After sample collection, the spacecraft will head back toward Earth before ejecting the Sample Return Capsule for landing in the Utah desert in Sept. 2023.

    NASA’s Goddard Space Flight Center provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for its Science Mission Directorate in Washington.

  11. Successful Second Deep Space Maneuver for OSIRIS-REx Confirmed

    July 3, 2018 -

    New tracking data confirms that NASA’s OSIRIS-REx spacecraft successfully completed its second Deep Space Maneuver (DSM-2) on June 28. The thruster burn put the spacecraft on course for a series of asteroid approach maneuvers to be executed this fall that will culminate with the spacecraft’s scheduled arrival at asteroid Bennu on Dec. 3.

    Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its TCM thrusters. Credit: University of Arizona

    The DSM-2 burn, which employed the spacecraft’s Trajectory Correction Maneuver (TCM) thruster set, resulted in a 37 miles per hour (16.7 meters per second) change in the vehicle’s velocity and consumed 28.2 pounds (12.8 kilograms) of fuel.

    Tracking data from the Deep Space Network provided preliminary confirmation of the burn’s execution, and the subsequent downlink of telemetry from the spacecraft shows that all subsystems performed as expected.

    DSM-2 was OSIRIS-REx’s last deep space maneuver of its outbound cruise to Bennu. The next engine burn, Asteroid Approach Maneuver 1 (AAM-1), is scheduled for early October. AAM-1 is a major braking maneuver designed to slow the spacecraft’s speed from approximately 1,130 to 320 miles per hour (506.2 to 144.4 meters per second) relative to Bennu and is the first of four asteroid approach maneuvers scheduled for this fall.

    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 of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s observation planning and processing. Lockheed Martin Space in Denver built the spacecraft and is providing spacecraft flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for its Science Mission Directorate in Washington.

  12. OSIRIS-REx Executes Second Deep Space Maneuver

    June 28, 2018 -

    Artist’s conception of NASA’s OSIRIS-REx spacecraft during a burn of its TCM thrusters. Credit: University of Arizona

    NASA’s OSIRIS-REx spacecraft executed its second Deep Space Maneuver today, which put the spacecraft on course for its scheduled arrival at the asteroid Bennu in December. The mission team will continue to examine telemetry and tracking data as they become available and will have more information on the results of the maneuver over the next week.

  13. Two Pieces of a Cosmic Puzzle: Hayabusa2 and OSIRIS-REx

    By Christine Hoekenga

    June 22, 2018 -

    It began with dust. Before there were asteroids, or planets, or people – about 4.6 billion years ago – a cloud of dust and gas swirled in the cosmos. At the center, a star began to form.

    With heat and shock waves, clumps of this ancient dust coalesced into droplets of molten rock called chondrules. These chondrules and dust became the building blocks of the Solar System. Eventually, chunks of material as large as asteroids, and even planets, formed from this cloud and organized according to the laws of physics around a newly born star: our Sun.

    Scientists believe one of these chunks became a protoplanet that eventually broke apart in a collision, giving rise to an asteroid that humans would one-day dub Bennu. Another (or perhaps the same) chunk produced another asteroid that would become known as Ryugu. Long before humans were around to give them names or contemplate their origins, both asteroids migrated from the asteroid belt between Mars and Jupiter into near-Earth space and settled into new orbits.

    It wasn’t until hundreds of millions of years later, in the 1800s, that human astronomers trained their telescopes on the sky and began identifying and studying asteroids. Fast forward to 1999. That year, the Lincoln Near-Earth Asteroid Research (LINEAR) survey discovered two near-Earth asteroids that would go on to become the targets for two robotic sample return missions: NASA’s OSIRIS-REx, launched in 2016 to study asteroid Bennu, and the Japanese Aerospace Exploration Agency’s Hayabusa2, launched in 2014 to study Ryugu.

    Even though humans have intently studied asteroids for centuries, we have had very few opportunities to get our hands on material directly from these cosmic time capsules. Meteorites, which are pieces of asteroids that have fallen to Earth, provide important clues about the early days of the Solar System, but they have two major limitations. First, scientists aren’t certain which parent bodies (asteroids) gave rise to most of them. Second, they are not clean, unaltered samples. After withstanding the heat of atmospheric entry, they land on the ground, where they become contaminated with materials from Earth and immediately begin to corrode.

    The only sample humanity has ever collected directly from an asteroid came back with JAXA’s Hayabusa Mission in 2010. That sample contains less than a milligram of particles from Itokowa, a “stony” asteroid with high silica content.

    Soon, though, we’ll have two new opportunities to study pristine asteroid material. This time the samples will come from the carbon-rich asteroids Bennu and Ryugu. These asteroids are of particular interest because they contain the very oldest material from the stellar nursery – and because carbon-bearing compounds are the basis of life as we know it. These samples, and the organic molecules they contain, will help shed light on some of humanity’s grand mysteries: Where did we come from? How did life develop on Earth?

    Both spacecraft will reach their respective destinations during 2018 – Hayabusa2 in June and OSIRIS-REx in December – and the missions fit together like two adjoining pieces of a cosmic puzzle. In combination, the data and discoveries from these two asteroid explorers will reveal a long-shrouded portion of the Solar System’s portrait.

    Mapping, navigating around, and collecting samples from small Solar System bodies are all relatively new endeavors for humanity, and the two mission teams have already been sharing ideas, data, and lessons learned for several years as part of a major partnership between NASA and JAXA. This exchange will continue as the two spacecraft operate in close proximity to their target asteroids. The OSIRIS-REx team will host Japanese scientists in the Science Operations Center at the University of Arizona, and OSIRIS-REx team members will travel to JAXA during Hayabusa2’s operations. They will share software, data, techniques for analysis, and aspects of each other’s cultural systems in the process. Ultimately, the two agencies will exchange portions of the returned samples as well.

    However, the two missions’ strategies for exploration are quite different. For starters, OSIRIS-REx will go into orbit around Bennu during two separate phases of asteroid operations. All told, the NASA spacecraft will spend more than a year and a half imaging and mapping Bennu with its suite of remote sensing instruments (cameras, spectrometers, and a laser altimeter) – a plan based partially on lessons learned from JAXA’s first Hayabusa mission. All of this data will be used to select a single sample site with high scientific interest and low risk to the spacecraft. After carefully rehearsing, OSIRIS-REx will move in close, extend its sampling arm, and touch the asteroid’s surface for just five seconds, using nitrogen gas to stir up and collect at least 60 grams of loose material.

    By contrast, Hayabusa2 will not actually orbit Ryugu. In fact, the JAXA spacecraft will spend only about three months mapping before it begins the process of collecting three separate, but smaller, samples from different geographic locations on Ryugu. In addition to remote sensing, Hayabusa2 will deploy a lander (called MASCOT) and two rovers (called MINERVA-II 1 and 2) and will use a projectile and small explosive during one sampling process to collect material from beneath the asteroid’s surface.

    Despite the differences, there are shared challenges, and both teams’ learning curves will be steep. Until now, neither asteroid has been seen up close, and they will likely have some surprises in store. The predictions made from the ground about their shapes, sizes, and compositions could turn out to be wrong. Ryugu is expected to be about 80 percent larger than Bennu (approximately 900 meters in diameter versus 500 meters in diameter), but both asteroids are much smaller than the planets and most other bodies that have been orbited or landed on by spacecraft. The small size and microgravity environment makes navigation and sampling that much more challenging.

    Both spacecraft are venturing into far-away and unknown territory and attempting feats that are new to humanity. For the most part, they will be on their own on the asteroid frontier, but the value of running complementary missions cannot be overstated. The scientific and cultural returns from the two missions combined is far more than double the value of each individual mission. The ability to make comparisons during planning, operations, and after the samples are returned reduces risk and make both missions exponentially better.

    And, like any expedition, the chances for success increase when there are two friendly explorers forging similar paths and learning side-by-side.

  14. Asteroid Bennu, as Seen from Earth

    By Christine Hoekenga

    May 1, 2018 -

    When Asteroid Bennu was discovered on Sept. 11, 1999 by the Lincoln Near-Earth Asteroid Research project (LINEAR), it was called 1999 RQ36 — a provisional designation assigned by the Minor Planet Center. After follow-up observations determined the asteroid’s precise orbit, it was issued the official number 101955, indicating that it was the 101,955th asteroid to be officially recognized.

    Bennu’s orbit brings it relatively close to Earth every six years (in 2018, for example, the asteroid comes within 0.352 AU or about 33 million miles), giving astronomers better opportunities to image the asteroid with telescopes. Additional ground-based observations of Bennu have been made a number times since the asteroid’s discovery, including these images captured by telescopes based in Arizona:

    Image of Asteroid Bennu from Earth Sept. 2005

    Sept. 17, 2005 — Six years after its discovery, Bennu was was observed by researchers using the 1.5-meter Kuiper Telescope at the University of Arizona. Credit: Carl Hergenrother/University of Arizona

     

     

    Image of Asteroid Bennu from Earth Sept. 2011

    Sept. 26, 2011 — A few months after NASA selected the OSIRIS-REx mission for funding to visit and sample Bennu, researchers using the 1.5-meter Kuiper Telescope at the University of Arizona observed the asteroid. Credit: Carl Hergenrother/University of Arizona

     

     

    Image of Asteroid Bennu from Earth May 2012

    April 20, 2012 — Researchers using the 1.5-meter Kuiper Telescope at the University of Arizona observed Bennu again in the spring of 2012. Credit: Carl Hergenrother/University of Arizona

     

     

    Image of Asteroid Bennu from Earth May 2012

    May 15, 2012 — Bennu was observed using the 1.8-meter Vatican Advanced Technology Telescope (VATT) on Mount Graham in Arizona in May 2012. Credit: Carl Hergenrother/University of Arizona/Vatican Observatory

     

    Scientists have also used radar data from the Arecibo Observatory in Puerto Rico and NASA’s Deep Space Network antenna in California to estimate Bennu’s shape and size. However, to this day, no one has ever seen or imaged the asteroid up close.

    That’s where OSIRIS-REx comes in.

    Starting in the summer of 2018, the spacecraft will begin imaging asteroid Bennu with its PolyCam imager. The first images will be similar to ground-based observations: the asteroid will appear as a point of light in the distance. As the spacecraft approaches Bennu, the images will become clearer and more detailed, eventually zooming in on the asteroid’s precise shape, size and surface features.

    The mission team will use these detailed images, along with data collected by the spacecraft’s other instruments, to create maps of Bennu and, ultimately to select the location where OSIRIS-REx will collect a sample of its surface material for return to Earth in 2023.

     

  15. A long, long way from home…

    February 14, 2018 -

     

    The OSIRIS-REx spacecraft captured this image of the Earth and Moon system using its NavCam1 imager on January 17 from a distance of 39.5 million miles (63.6 million km). Earth is the largest, brightest spot in the center of the image, with the smaller, dimmer Moon appearing to the right. Credit: NASA/Goddard/University of Arizona/Lockheed Martin

    As part of an engineering test, the OSIRIS-REx spacecraft captured this image of the Earth and Moon using its NavCam1 imager on January 17 from a distance of 39.5 million miles (63.6 million km).  When the camera acquired the image, the spacecraft was moving away from home at a speed of 19,000 miles per hour (8.5 kilometers per second).

    Earth is the largest, brightest spot in the center of the image, with the smaller, dimmer Moon appearing to the right. Several constellations are also visible in the surrounding space. The bright cluster of stars in the upper left corner is the Pleiades in the Taurus constellation. Hamal, the brightest star in Aries, is located in the upper right corner of the image.  The Earth-Moon system is centered in the middle of five stars comprising the head of Cetus the Whale.

    NavCam1, a grayscale imager, is part of the TAGCAMS (Touch-And-Go Camera System) navigation camera suite.  Malin Space Science Systems designed, built, and tested TAGCAMS; Lockheed Martin integrated TAGCAMS to the OSIRIS-REx spacecraft and operates TAGCAMS.

     

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