On Nov. 5, the spacecraft successfully executed a trim maneuver (AAM-3a) to re-target conditions for the AAM-4 maneuver scheduled for Nov. 12. It also realigned the spacecraft’s trajectory with the precise approach corridor needed for the PolyCam shape model imaging planned over the next several weeks. The 6 cm/s maneuver was only the second burn utilizing the spacecraft’s Attitude Control System (ACS) thrusters, which are capable of velocity changes as small as 1 cm/s.
On Nov. 7, the Mission Planning Board evaluated the mission’s readiness to proceed from Approach Phase into Preliminary Survey Phase and determined that OSIRIS-REx is a GO. Barring any anomalies on the flight system or any unforeseen Bennu surprises, the spacecraft will “arrive” at Bennu on Dec. 3 and begin Preliminary Survey’s hyperbolic flyovers of the poles and equator.
The science payload also executed the following observations in the past week: OCAMS MapCam Daily Phase Function, OTES Full Disk Integrated Spectroscopy, OVIRS Full Disk Integrated Spectroscopy, OVIRS Solar Calibration, OCAMS PolyCam Natural Satellite Search, OCAMS MapCam Natural Satellite Search, and TAGCAMS Natural Satellite Search ride-along with OpNavs.
OSIRIS-REx has had another busy period of science and spacecraft operations. From Oct. 25 to Nov. 5, the OCAMS cameras made observations for the Daily Phase Function science campaign. The images from this campaign provide data to measure changes in light reflected from Bennu’s surface as the Sun illuminates the asteroid from different angles. These observations will provide information on Bennu’s albedo and the way light is reflected from the asteroid’s surface.
On Oct. 25, the five Frangibolts keeping the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) arm against the spacecraft structure were successfully released. On Oct. 26, the Motor Articulation Control Module (MACM-2) card was powered on for the first time in flight. The three motors were effectively commanded to move the TAGSAM arm out of the launch container and into the parked position.
The Natural Satellite Search campaign also continued during this time using both the PolyCam and MapCam cameras of the OCAMS instrument, as well as the TAGCAMS navigation cameras as ride-alongs.
On Oct. 29, the spacecraft executed its third Asteroid Approach Maneuver (AAM-3), slowing the spacecraft by approximately 5.13 m/sec. This was also the mission’s first two-part burn maneuver, which accommodated constraints for the science instruments to not be pointed too closely to the Sun.
On Oct. 29, PolyCam also obtained images of Bennu to provide a “super-resolution” view of the asteroid that exceeded the best ground-based data collected.
This week, the OSIRIS-REx spacecraft executed its third Asteroid Approach Maneuver, slowing the spacecraft’s speed down to .24 mph (.11 m/sec).
This last week was very busy for the mission. On Oct. 15, the spacecraft successfully executed its second Asteroid Approach Maneuver (AAM-2), which slowed its rate of approach toward Bennu by approximately 305 mph (137 m/s) and burned around 186 lbs. (84.4 kg) of fuel. There are two more AAMs scheduled over the next month to further slow and more precisely target the spacecraft’s trajectory toward Bennu. The final two maneuvers are much smaller than AAMs 1 and 2, and will use the spacecraft’s Trajectory Correction Maneuver (TCM) engines instead of its Main Engines.
On Oct. 17, the OSIRIS-REx team jettisoned the cover that protected the TAGSAM head during launch and early flight. The team used several methods to confirm that the cover ejection was successful. Directly before the deployment, the spacecraft executed its third sample mass measurement (SMM-3) spin to measure the spacecraft’s mass properties while the cover was still attached. The day after the deployment, the spacecraft executed SMM-4, which confirmed that the spacecraft’s mass had decreased by around 2.67 lbs. (1.21 kg) from the previous day. The team was also able to confirm the cover ejection through telemetry indicating changes in thermal signatures and forces on the spacecraft.
On the mission’s science side, the spacecraft also continued with its Bennu Phase Function Observation campaign this week. Bennu now appears larger than a pixel in the PolyCam imager’s field of view, and the team is looking forward to the next few weeks as the asteroid’s shape is finally revealed.
This week, the OSIRIS-REx spacecraft executed its second Asteroid Approach Maneuver, as it continues slowing down while approaching Bennu.
New tracking data confirm that the spacecraft completed its first Asteroid Approach Maneuver (AAM-1) on Oct. 1, starting the final approach to Bennu. The main engine burn slowed the spacecraft speed by 785.831 miles per hour (351.298 meters per second) and consumed 532.4 pounds (241.5 kilograms) of fuel.
From the beginning of the mission’s science operations on Aug. 17 through AAM-1, PolyCam obtained optical navigation images (OpNavs) of Bennu on a Monday, Wednesday and Friday cadence. After AAM-1, PolyCam is taking daily OpNavs as the spacecraft continues to close in on the asteroid.
This last week the spacecraft’s MapCam camera also began taking daily Phase Function images. These images support the mission’s science requirement to measure changes in light reflected from Bennu’s surface as the Sun illuminates the asteroid across a range of angles. These observations provide information on Bennu’s albedo and the way light reflects under various observing conditions.
This week, the OSIRIS-REx spacecraft executed its first Asteroid Approach Maneuver to put it on course for its scheduled Bennu arrival in December.
As of today, OSIRIS-REx is approximately 480,000 km from Bennu and is 6 days from executing Asteroid Approach Maneuver 1 (AAM-1) on Oct. 1. AAM-1 is the first of four major maneuvers that will slow the spacecraft’s velocity on its final approach to Bennu. The spacecraft is currently flying at approximately 490 m/s (~1,100 mph), and AAM-1 will slow the spacecraft’s rate of approach to Bennu by 350 m/s (~780 mph) to 140 m/s (~310 mph).
This last week, the mission’s navigation team delivered the preliminary designs for AAM-1, and the final design will be completed and radiated to the spacecraft in the upcoming week.
On Sept. 14, the spacecraft’s REXIS instrument opened its Radiation Cover and REXIS now has a clear view of space for the first time. The Radiation Cover protected the detectors from radiation damage during the cruise to Bennu, but it also blocked the aperture of the instrument. With OSIRIS-REx nearing Bennu, the mission team opened the cover to enable REXIS to observe external calibration targets like the Crab Nebula, as well as ultimately the asteroid.
The Radiation Cover had been held shut by a Frangibolt since before launch. On Friday, the Frangibolt was actuated by heating it up, which expanded a shape-memory alloy cylinder, breaking the titanium bolt holding the cover shut. By inspecting heater and temperature telemetry and comparing the difference between spectra taken before and after the Frangibolt firing, the REXIS team was able to determine that the cover opened successfully and the instrument is now seeing the cosmic X-ray background. Going forward, REXIS will take measurements on several astrophysical X-ray sources in preparation for observations of Bennu starting next summer.
This last week the OSIRIS-REx spacecraft continued its approach toward Bennu. Now that we have visually acquired the asteroid, the PolyCam camera images Bennu three times a week to provide data to the navigation team. At a distance of 1.1 million km, Bennu appears as just a dot. However, the navigation team can still use these images to calculate the spacecraft trajectory and refine Bennu’s orbit.
This last week the mission’s Science Operations Planning Group held the tactical kickoff for the upcoming Natural Satellite Search. The mission operates on an 8-week science planning schedule, so between now and the search’s commencement on Oct. 23, the finalized commands for the activity will be built, tested, and radiated to the spacecraft. Beyond the inherent science value of the possible discovery of natural satellites at Bennu, the search is key to assess the spacecraft’s safety while it operates in the area around the asteroid.
This last week the team processed and released its first set of images of the mission’s target asteroid Bennu. The spacecraft’s PolyCam camera took the images from a distance of approximately 2.2 million km. Now that OSIRIS-REx has come into instrument range of Bennu, the spacecraft’s science payload will make regular observations of Bennu and its surroundings as it continues to approach the asteroid.
Last week marked the beginning of OSIRIS-REx’s Approach Phase, which is the first phase of mission asteroid operations. Visit the Asteroid Operations page to discover how the spacecraft and the mission team will be exploring Bennu over the next few years.
This last week, the mission team ran a checkout of the spacecraft’s two GNC (Guidance, Navigation and Control) LIDAR systems. These sensors are designed to provide navigational information while the spacecraft is operating in close proximity to the asteroid, in particular during the TAG sampling maneuver. The LIDAR system calculates the distance to Bennu by bouncing laser pulses off Bennu’s surface and measuring the time it takes for the light to return to the detector. Because there were no targets in the vicinity to bounce the laser off during the test, this LIDAR checkout solely focused on system outputs. Preliminary results indicate that the checkouts executed as expected.
The mission team also spent this last week preparing for the kick-off of asteroid operations, which is scheduled to occur on Aug. 17 when the spacecraft’s OCAMS camera takes its first image of Bennu.
On July 30-31, the spacecraft conducted another Sample Mass Measurement (SMM) calibration activity. After sample collection, the mission team will use the SMM pirouette to measure the mass of the collected regolith in the TAGSAM head. The team is awaiting the downlink of the complete data set from the spacecraft to be able to analyze the performance of the spin maneuvers, but preliminary data indicates that they executed as expected.
This last week, the mission team assessed that the second week of the Launch+22 months instrument checkouts and calibrations proceeded as expected. This was the last set of checkouts and calibrations the spacecraft will execute before the beginning of Approach Phase on August 17 and the resulting Bennu imaging campaign.
Since launch on September 8, 2016, the OSIRIS-Rex spacecraft has travelled 1.73 billion km, and it has around 302 million km to travel before its scheduled arrival at Bennu on December 3.
Last week, the Launch+22 months instrument checkouts and calibrations progressed through their second week of observations. The mission team also assessed that the instruments exercised during the campaign’s first week, OCAMS, OVIRS and REXIS, operated as expected.
Also last week, the spacecraft passed the 4 million km range-to-Bennu mark, and is now 3.8 million km from the asteroid.
This week the team began a two-week campaign of instrument checkouts and calibrations. The mission exercises the spacecraft’s payloads approximately every six months during flight to ensure that all instruments are working as expected. This also provides an opportunity to collect additional calibration data on each instrument, which is used to further refine the science data ground processing. These checkouts are the final checkouts before the Approach phase begins mid-August.
Further reconstruction analysis this week by the mission teamconfirmed that the spacecraft’s deep space maneuver on June 28 was successful and closely followed the team’s design and predicts. Also on Earth, the Science Operations Planning Group (SOPG) is in the midst of planning operations for the first three weeks of Approach Phase, which will start on August 17.
On June 28, the spacecraft executed the second deep space maneuver of its outbound cruise. Preliminary analysis indicates that the spacecraft performed the maneuver as planned, and the team is conducting more detailed analysis to determine the maneuver’s exact results.
On June 19, the Science Operations and Planning Group (SOPG) held the tactical kickoff for the first week of Approach Phase, which commences August 17. This means that the day-to-day operational planning of the mission’s Bennu science operations has begun.
This week the OSIRIS-REx mission team has also been enthusiastically watching our JAXA partner mission, Hayabusa2, return its first images of the asteroid Ryugu. In these images, Ryugu has shown itself to be shaped remarkably similarly to what Bennu is expected to look like. OSIRIS-REx and Hayabusa2 are working collaboratively on their respective asteroid sample return missions to reduce risk and increase the science knowledge obtained.
The mission team this week continued preparations for the spacecraft’s arrival at Bennu by holding series of technical interchange meetings (TIMs) focusing on asteroid proximity operations. The team also held an initial walkthrough of the Touch-and-Go (TAG) sampling sequence.
The spacecraft is now less than 7 million kilometers from Bennu and has 388 million km left to travel as it chases down the asteroid for its scheduled arrival this December.
This past week, OSIRIS-REx continued nominal operations en route to asteroid Bennu. The spacecraft has been in space for 640 days and is currently 56.4 million km from Earth.
On the ground, several members of the OSIRIS-REx team were recognized with 2018 NASA Agency Honor Awards:
- Peter Antreasian – Exceptional Public Service Medal
- Coralie Jackman and Devin Poland – Early Career Public Achievement Medal
- Dennis Reuter – Distinguished Service Medal
- OSIRIS-REx Earth Gravity Assist (EGA) Team – Group Achievement Award
- OCAMS Instrument Team/Bashar Rizk – Silver Achievement Medal
OSIRIS-REx continued nominal operations in support of Outbound Cruise Phase this week, and the spacecraft team is planning Deep Space Maneuver-2 — the last significant maneuver before Approach Phase — scheduled for June 28. The instrument teams are planning the Launch+22 month instrument checkouts, which will execute in mid-July.
The range between OSIRIS-REx and Bennu is currently 8.5 million km. Because both the spacecraft and the asteroid are orbiting the Sun, OSIRIS-REx has 417 million km left to travel before arriving at Bennu in December.
This last week the mission marked a major milestone. On May 22, the Science Operations Planning Group (SOPG) held the kickoff of the mission’s Approach Phase. The SOPG Approach Kickoff marked the official start of detailed planning for the spacecraft’s instrument operations to study Bennu, which will begin on Aug. 17. The first instrument operation being planned is the spacecraft’s first observation of Bennu, which will be taken by the PolyCam imager from a distance of approximately 2 million km.
Last week the mission team conducted a successful checkout of the spacecraft’s Medium Gain Antenna (MGA). With this test, all of the spacecraft’s antennas have now been used in flight.
OSIRIS-REx has four antennas for communicating between the spacecraft and Earth. The largest, the High Gain Antenna (HGA), has the highest data rate but has a narrow gain pattern, meaning that it must be directly pointed at Earth for successful transmission. The MGA has a larger pattern, but a lower data rate. In favorable geometries, it will be used to communicate status telemetry back to Earth during the sampling maneuver. The two Low Gain Antennas (LGAs) provide near complete coverage and very low data rate communications. The LGAs are especially useful for transmitting progress telemetry during events, such as maneuvers, when the spacecraft’s other antennas aren’t facing Earth.
On May 7 and 9, the spacecraft conducted its second Sample Mass Measurement (SMM) pirouette activity. The SMM pirouette allows the mission team to measure the mass of the collected sample once it is in the TAGSAM head. Before sample collection, the spacecraft will do a number of spin maneuvers while the sample head is still empty. After sample collection, OSIRIS-REx will back away from the asteroid surface and pirouette again. The ground team will then compare the spacecraft’s mass properties for the “empty” and “full” spins to yield a basic estimate of the collected sample’s mass. The SMM maneuver this week provided the team with calibration information for the activity.
OSIRIS-REx continued nominal operations last week. The spacecraft is currently traveling at a speed of 5.86 km/sec (21,090 km/hr) relative to Earth, and 2.19 km/sec (7,883 km/hr) relative to Bennu. It has approximately 482 million km left in its journey before it arrives at the asteroid later this December.
Last week was the final execution week of the Operational Readiness Test (ORT), with the mission team simultaneously supporting nine weeks of parallel planning to simulate late Approach Phase, Preliminary Survey Phase, and part of Orbital A Phase. The week concluded with the simulated uplink of execution commands to the spacecraft. This ORT proved to be an extremely valuable exercise involving the entire operations team and has provided significant experience in the various stages of mission planning, implementation, and execution that will begin in earnest with the start of asteroid operations later this year.
This week the mission received good news regarding the Sample Return Capsule (SRC) outgassing mitigation campaign that was implemented last fall to remove excess water from the SRC. Over the last few months, the spacecraft has been placed into various positions to expose different sides of the capsule to the Sun in order to bake the moisture out. After completing the analysis of the various maneuvers, the navigation team this week confirmed that there is no longer detection of outgassing at a level that could interfere with the spacecraft’s navigation requirements during Bennu proximity operations.
OSIRIS-REx continued outbound cruise operations this last week. On the ground, members of the navigation team worked through the results of a Navigation Training Exercise (NTE) test on asteroid shape modeling. The test was designed to demonstrate the team’s readiness to perform landmark optical navigation techniques during asteroid proximity operations. This means the team would be able to navigate the spacecraft using Bennu’s landmarks as a guide instead of using star fields. Landmark navigation provides more precise and timely information on the spacecraft’s location around Bennu, which improves mission safety and efficiency.
The spacecraft remained in nominal operations this week. On the ground, the team continued planning asteroid proximity operations for execution starting late summer, while also participating in the ongoing Operational Readiness Test simulation.
On April 4, the team uplinked a patch for the Relative Asteroid Target List up to the spacecraft. This upgrade will allow the team to point the spacecraft using its sense of nadir (the location directly below the spacecraft) when taking science observations. Currently, the spacecraft uses absolute (instead of relative) pointing, so each time the ground team sends a new ephemeris, planned observations must be updated. This new capability will greatly reduce the number of late information updates required for observations and will make observation products reusable.
As of this week, OSIRIS-REx has travelled over 1.5 billion km since its launch in Sept. 2016. It is currently 47.7 million km from Earth and has a little over .5 billion km left to travel until it reaches the asteroid Bennu.
This last week the mission team continued the analysis of data obtained during the Launch + 18 months payload checkout and extended OCAMS and TAGCAMS calibrations. The team also concurrently worked through week 5 of the Operational Readiness Test simulation, which replicates the mission’s operations schedule for late Fall.
The spacecraft passed the 20 million km range-to-Bennu mark this week and is currently 19.5 million km from Bennu.
The OSIRIS-REx spacecraft continued to operate nominally this last week. The extended calibration opportunity for the OCAMS and TAGCAMS instruments began on March 15 and ran through March 24. This exercise allowed both instruments to run through a full slate of imaging activities in advance of asteroid proximity operations, which start later this summer.
The OSIRIS-REx spacecraft is currently travelling 5.57 km/sec (20,052 km/hr) relative to Earth.
The Launch + 18 Months payload checkout and calibration campaign finished this last week with the REXIS checkout on March 13. The mission is now in the midst of extended calibrations for the OCAMS and TAGCAMS cameras, which will run until the end of this week. The OVIRS spectrometer will also get an opportunity to collect extra calibration data as a ride-along activity during a portion of the extended exercise.
As of today, the spacecraft is a little under 23 million km from Bennu and still has almost 541 million km left to travel before catching up to the asteroid this fall.
This last week was a busy one for the mission. Throughout the week, the spacecraft executed the Launch + 18 Months payload checkout and calibration campaign. Twice a year during Cruise Phase, the mission exercises its payload – the science and navigation instruments – to ensure they are working as expected and to continue instrument calibrations in preparation for asteroid operations. The campaign extends over the next two weeks to provide continued calibration opportunities for OCAMS (the science cameras) and TAGCAMS (the navigation cameras).
This week the spacecraft also performed a checkout of newly approved downlink rates for communications back to Earth, and it completed the last of the scheduled SRC outgassing activities. The team on the ground is also progressing through the nine-week Super ORT (Operational Readiness Test) simulation exercise in parallel with real world activities.
This last week the OSIRIS-REx team commenced an extensive Operational Readiness Test (ORT), known as the Super ORT, in preparation for asteroid proximity operations. Over the next nine weeks, the mission’s planning teams, instrument teams, and ops teams will be simulating the full range of activities required to support the mission during the last week of Approach Phase (currently scheduled for late November). By rehearsing the actual operations the mission team will perform once OSIRIS-REx arrives at Bennu, the Super ORT will thoroughly exercise the mission’s team, tools, and processes.
Flight operations continued normally this last week. The mission team on the ground is in the midst of preparing the Launch + 18 Months calibration campaign scheduled for execution in early March.
OSIRIS-REx is currently 61.6 million km from Earth.
This week the spacecraft conducted activities that validated its ability to perform some of the maneuvers required for sample collection. On Feb. 12, the spacecraft conducted a TAG (Touch-and-Go) Backaway Maneuver, demonstrating the propulsive maneuver the spacecraft will use to leave the asteroid’s surface after sampling. On Feb. 15 and 16, the spacecraft ran a checkout of its two precision LTR (Low Thrust Rocket-Engine-Assembly) Thrusters. These tiny rocket engines will be used to make fine velocity adjustments when OSIRIS-REx is in orbit about Bennu, such as the spacecraft’s critical orbit phasing burn to set up the proper orbit departure point leading to sample acquisition.
OSIRIS-REx is currently 30 million km from Bennu and has 648 million km to left to travel before it reaches the asteroid.
This last week, spacecraft operations continued normally. On the ground, further analysis of the 80 TAGCAMS images from the January stray light characterization activity discovered that some of NavCam1’s testing images had captured the Earth and Moon system. The images were taken from over 63 million km away while the spacecraft was moving away from Earth at approximately 8.6 km/second.
Flight operations continued normally this last week. The team finished up the OSIRIS-REx Laser Altimeter (OLA) regression test checkout with the new flight software in place and are now running an analysis of the results. The second in-flight checkouts of LIDARs 1 and 2 were also run on January 29 and February 2.
As of today, the spacecraft has traveled a total of 1.35 billion kilometers since launch in September 2016.
This last week the team uploaded new flight software for the OSIRIS-REx Laser Altimeter (OLA) to the spacecraft and conducted an instrument checkout, which confirmed that it is operating as expected. On the ground, the spacecraft’s instrument scientists and engineers met at the OREx Science Processing and Operations Center (SPOC) at the University of Arizona to help finalize the mission’s science operations schedule of activities, which will begin in August 2018.
The spacecraft is currently travelling approximately 29,072 km/hr (18,064 mph) relative to Earth.
On January 16-17, the mission team conducted a stray light characterization activity involving the OCAMS (OSIRIS-REx Camera Suite) instrument and the TAGCAMS navigation cameras.
Stray light occurs whenever sunlight shines on the OSIRIS-REx science deck and the sun’s rays bounce off its taller structures, such as PolyCam, OTES, and the Sample Return Capsule. Through a series of second, third and higher-level reflections, this redirected light finds its way into the cameras’ fields of view and produces glare in the images, especially for long exposures.
The goal of the stray light test is to study and determine the direction and amount of unwanted light that is scattered into the cameras. The Image Processing Working Group uses these stray-light background patterns to correct images that are acquired when the science deck points toward the Sun, such as during the search for possible dust and gas plumes around Bennu.
The amount of stray light that the spacecraft’s cameras have detected is within normal system performance requirements. This stray light characterization study is simply an effort to understand the behavior of the system in flight in the real space environment, which couldn’t be fully realized on the ground or in computer simulations before launch.
Last week, OSIRIS-REx continued normal Outbound Cruise operations. On Jan. 10, the spacecraft performed another tilting maneuver in support of the ongoing outgassing campaign. On Jan. 15, the spacecraft resumed communicating back to Earth over its High Gain Antenna, following a four-month period limited to the Low Gain Antennas with attendant low downlink rates.
The spacecraft’s one-way light time for communications back to Earth is currently 3 minutes and 27 seconds.
On Jan. 4 and 5 the mission continued outgassing campaign activities by again rotating the spacecraft to expose the SRC to the sun. The mission team will study the results of this activity over the next few weeks to determine whether the campaign has removed sufficient water from the capsule or if further outgassing operations are required.
As of today, the spacecraft has traveled 1.3 billion km and has 721 million km left to travel before it is scheduled to arrive at Bennu on Dec. 3, 2018.
On Dec. 20, the mission transitioned into Outbound Cruise sub-phase 5, which is the final sub-phase of Outbound Cruise operations. To mark the transition, the spacecraft returned to using the +X Low Gain Antenna (LGA) for its communications back to Earth. The spacecraft had previously been communicating over the –X LGA.
The next mission operations transition will be into Approach Phase, which begins Aug. 17, 2018, when the spacecraft is approximately 2 million km from Bennu.
The spacecraft maintained its trajectory this last week as it continues on its outbound journey to Bennu. On Dec. 8, the spacecraft conducted a Sample Mass Measurement (SMM) pirouette activity as part of the ongoing outgassing campaign.
The SMM pirouette was originally designed to help the mission team measure the mass of the sample after it is collected from Bennu’s surface in 2020. Once the sample is in the TAGSAM head, OSIRIS-REx will back away from the asteroid surface and perform a spin maneuver. The ground team will then compare the spacecraft’s mass properties with those of a previous, sample-less spin in order to yield a basic estimate of the collected sample’s mass. For the outgassing campaign, however, the mission team employed this SMM spin maneuver to expose different parts of the spacecraft to the Sun in order to further remove water from the spacecraft. This exercise will prevent water from interfering with the spacecraft’s balance when it performs the maneuver after sampling. Preliminary reports indicate that the activity proceeded as expected.
The spacecraft has travelled 1.2 billion km since launch and will travel another 781.7 million km before it reaches Bennu.
Last week, OSIRIS-REx continued Outbound Cruise operations. The spacecraft is currently 47.6 million km from Earth and is executing a program designed to study and reduce the presence of water on the spacecraft.
During routine in-flight testing of the spacecraft’s thermal properties earlier this year, the mission’s navigation team noticed an unexpected minor acceleration of the spacecraft when the Sample Return Capsule (SRC) was exposed to sunlight. The mission team determined that this small thrust was caused by the outgassing of water that had been adsorbed by the SRC’s heat shield and backshell before launch. Retention of water in blanketing and other materials – and the subsequent outgassing of this water – occurs with all spacecraft. For OSIRIS-REx, it was determined that when the SRC is exposed to the Sun at a distance of <1.0 AU, this trapped water escapes and imparts a small thrust. While this small thrust would not be a problem for other missions, the gravity at the target asteroid Bennu is low enough that even this small amount of thrust could make orbital operations more difficult for OSIRIS-REx.
To better understand the outgassing effects on the spacecraft’s trajectory – and to bake out much of the remaining water before the spacecraft arrives at Bennu – the OSIRIS-REx mission team designed an outgassing program for execution starting earlier this fall. The choice of timing took into account both the spacecraft’s proximity to the Sun (<1.0 AU) and the fact that there were no science activities planned during this period. The outgassing program is being run concurrently with Outbound Cruise operations and does not affect the timing of the spacecraft’s arrival at Bennu.
Starting in mid-October, the spacecraft has been placed into various attitudes to expose different parts of the SRC to direct sunlight and initiate outgassing. Priority is given to the portions of the SRC that will face the Sun during asteroid proximity operations. The mission team has been able to detect and measure the rate of outgassing at each attitude and has determined that water is being removed as expected. The goal is to reduce the outgassing to the point where the spacecraft can fly the planned baseline trajectories around Bennu without modifications, and preliminary indications show that the program is progressing toward this goal. The program is scheduled to run through early January 2018.
The spacecraft continues to operate nominally. This last week the team updated some of the spacecraft’s onboard navigation files and, on Nov. 20, OSIRIS-REx’s downlink rate increased to 2 kbps from 200 bps.
OSIRIS-REx has travelled 1.17 billion km since launch and still has 824 million km to go until it arrives at Bennu.
Last week OSIRIS-REx continued Outbound Cruise operations. The spacecraft is currently 39 million km from Earth and 55 million km from Bennu.
Last week the spacecraft maintained normal operations for its Outbound Cruise Phase. On Nov. 13, the spacecraft’s communications downlink rate decreased to 200 bps from 10 kbps. The spacecraft continues to communicate back to Earth through its low gain antenna (LGA).
On the ground this last week, the OSIRIS-REx Science Team gathered in Tucson, Ariz. for its bi-annual meeting. This meeting focused on further refining the science planning processes that will be implemented when the spacecraft arrives at Bennu.
OSIRIS-REx continued normal Outbound Cruise operations last week. As of today, the spacecraft is 57 million km from Bennu, traveling at 8 km/sec relative to Earth. The one-way light time for transmissions from the spacecraft back to the ground is 100 seconds, which is an increase of 15 seconds in the last week. The spacecraft’s communications downlink rate remains at 10 kbps.
Last week the spacecraft maintained normal operations for its Outbound Cruise Phase. OSIRIS-REx is currently 25.6 million km from Earth and is traveling at approximately 28,000 km/h relative to Earth. One-way light time for transmissions from the spacecraft back to the ground is 85 seconds.
This past week, the mission took advantage of the spacecraft’s long outbound cruise to study the spacecraft’s thermal profile. As part of the exercise, the spacecraft was placed into certain orientations that it will employ during asteroid proximity operations in order to more precisely determine the thermal properties of each part of the spacecraft. As different spacecraft components were exposed to the Sun, the team measured how quickly they warmed and cooled. This in-flight characterization of OSIRIS-REx’s thermal properties will help the team more accurately predict the spacecraft’s thermal state while the spacecraft is operating close to Bennu.
Back on Earth, the ground team continues to be busy planning spacecraft operations and science observations for Bennu proximity operations, which will begin in August 2018 and continue through sample collection, scheduled for July 2020.
As of Oct. 23, the OSIRIS-REx spacecraft is traveling at approximately 25,000 kph relative to Earth. The spacecraft is approximately 17 million km from Earth and 57.7 million km from Bennu. But because Bennu is orbiting around the Sun and isn’t stationary, the spacecraft must still travel 948 million km before it can catch up to the asteroid.
On Oct. 16, the spacecraft’s communications downlink rate decreased to 10 kbps. Because of the low data rates and other mission planning activities, no science observations are planned through Jan. 7, 2018.
Last week, the OSIRIS-REx spacecraft continued on its new post-EGA trajectory toward Bennu. A REXIS Solar X-Ray Monitor testing and calibration activity began Oct. 9 and ran through Oct. 12. On Oct. 7, the spacecraft’s communications downlink rate decreased to 40 kbps from 200 kbps. The spacecraft continues to communicate back to Earth through its low gain antenna (LGA).
As of Oct. 16, the OSIRIS-REx spacecraft is approximately 12.9 million km from Earth and has traveled around 1.03 billion km since launch. It has another 970 million km to travel before it reaches Bennu.
The mission’s instrument teams and science working groups continue to actively process EGA science observations for the OCAMS, OVIRS, OTES and TAGCAMS instruments. Early indications show outstanding performance of the instruments, giving confidence that they will operate as designed at Bennu. Although the EGA maneuver and subsequent observations went smoothly overall, the science operations team is looking at lessons learned from EGA on both planning and ground tools to assess whether there are further improvements that could be made for Bennu operations.
As of Oct. 9, the OSIRIS-REx spacecraft is approximately 8.8 million km from Earth and its one-way light time is around 30 seconds.
Following a successful Earth Gravity Assist on Sept. 22, the spacecraft engaged its OCAMS and TAGCAMS cameras and OTES and OVIRS spectrometers on Sept. 22, Sept. 25 and Sept. 28 to observe the Earth and Moon. The instruments operated nominally and the mission team was able to use the opportunity to exercise its science operations procedures and calibrate the spacecraft’s instruments. Images and spectra of Earth and images of the Earth and Moon were also released. A final day of observations is scheduled for Oct. 2.
The mission’s navigation team determined that the spacecraft’s post-EGA trajectory was on course as planned. As a result, the trajectory correction maneuver (TCM-6) scheduled for Oct. 4 was cancelled.
On Friday, the OSIRIS-REx spacecraft completed its planned Earth Gravity Assist.
Last week, the OSIRIS-REx spacecraft maintained nominal operations as it continued on a trajectory toward Earth for its scheduled Sept. 22 Earth Gravity Assist (EGA). On Sept. 14, the spacecraft’s communications downlink rate increased to 300 kbps from 200 kbps as the spacecraft’s distance to Earth continues to shrink. The spacecraft is currently communicating through its low gain antenna (LGA).
As of Sept. 18, the spacecraft is 2.6 million km from Earth and its one-way light time is around 9 seconds.
This week, OSIRIS-REx’s navigation team determined that the spacecraft’s 23 Aug. trajectory correction maneuver (TCM-3) accurately set the spacecraft on the correct trajectory for its Sept. 22 Earth Gravity Assist (EGA). This means that there will be no need to execute TCM-4 or TCM-5, which were originally scheduled to further target the spacecraft at the optimal EGA aim-point.
Preparations for EGA continue for the team on the ground. In particular, the instrument teams are getting ready for science observations of Earth and the Moon as the spacecraft swings by Earth and continues on a new orbital plane out toward Bennu.
As of Sept. 11, the spacecraft is 6.5 million km from Earth, having traveled 933.9 million km since launch on Sept. 8, 2016.