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.