Emily LakdawallaAug 17, 2016

OSIRIS-REx launch preview

Launch day is coming for NASA's next interplanetary explorer! OSIRIS-REx is on schedule for launch on September 8, 2016 at 19:05 EDT (16:05 PDT, 23:05 UTC) from Cape Canaveral Air Force Station. It will take two years for the spacecraft to enter orbit at near-Earth asteroid 101955 Bennu, and plans to return samples to Earth on September 24, 2023. The launch comes at a time when NASA has ten active missions but few other launches: OSIRIS-REx is the first NASA planetary launch since MAVEN in 2013, and will be the last until InSight in 2018. A press briefing held today summarized the mission's goals, capabilities, and plans:

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Between now and launch, the spacecraft still needs to be attached to the payload adapter and enclosed in the protective fairing, then lifted to the top of the Atlas rocket, which is already on top of the launch pad. Those activities should begin on the 23rd. Stay tuned to the Kennedy Space Center's Flickr photo feed for pictures of the mission's progress toward launch.

The mission press kit details the launch plans. The launch period opens on September 8 and closes October 12. There is a 120-minute window in which the launch can take place on any given day. The launch vehicle is an unusual Atlas V rocket with only a single strap-on booster. Once the Atlas launches, it should all be over very quickly; spacecraft separation comes less than an hour after launch. Here's the nominal timeline for the first moment of the first day of the launch period:

EventTime (rel,
Jettison of the single solid rocket booster02:19.023:07:1919:07:1916:07:19
Common Core booster cutoff04:02.823:09:0319:09:0316:09:03
Centaur separation04:08.823:09:0919:09:0916:09:09
First Centaur ignition (burn time: 8min 3.7s)04:18.823:09:1919:09:1916:09:19
Payload fairing jettison04:26.823:09:2719:09:2716:09:27
First Centaur cutoff (coast time: 21min 25.7s)12:22.523:17:2219:17:2216:17:22
Second Centaur ignition (burn time: 6min 50.4s)33:48.223:38:4819:38:4816:38:48
Second Centaur cutoff (coast time: 15min)40:38.623:45:3919:45:3916:45:39
Spacecraft separation55:38.600:00:3920:00:3917:00:39
Solar panels open (approx.)58:38.600:03:3920:03:3917:03:39
Rotate to comm attitude12:38.600:17:3920:17:3917:17:39

Current plans are for the science instruments to be checked out 14 days after launch, mission engineers said at a press briefing held today. They do not plan to use the instruments to observe Earth upon departure, because they'll have an opportunity to perform Earth observations during the flyby that comes a year after launch, on September 22, 2017. After that, the next world that OSIRIS-REx will see will be Bennu, which will appear as a one-pixel dot to the highest-resolution PolyCam camera in August, 2018. The mission will spend two years performing reconnaissance of the asteroid before attempting sampling in July 2020, and will depart in March, 2021.

One detail shared at today's press briefing that I particularly enjoyed was the plans for curation of the returned sample. OSIRIS-REx could return anywhere between 60 and 2000 grams of sample, depending on unknown characteristics of the surface of the asteroid. It'll be the most material returned in a sample return mission since the lunar missions of 1976. Once they have brought the sample back to Earth, they plan to send 4% of the material to Canada, which is a partner on the mission. They'll also send 0.5% of the material to JAXA, reciprocating the Hayabusa team's generosity with their precious micrograms of sample from Itokawa. But the majority of the sample -- 75% of it -- will be left untouched, preserved as pristine as possible against the development of future analysis techniques that can yield new results from old samples, much as we're still making discoveries from Apollo samples today.

The Spacecraft

The main body of the OSIRIS-REx spacecraft has heritage that runs through MAVEN and Juno back to Mars Reconnaissance Orbiter. The sample return capsule is a near-duplicate of the one from Stardust. OSIRIS-REx carries 6 science instruments. You can download cool instrument schematics from the mission website.

  • OSIRIS-REx Camera Suite (OCAMS): Three cameras, PolyCam, MapCam, and SamCam. PolyCam is for high-resolution imaging, both long-range (providing the first resolved views of Bennu) and close-up (for sample site reconnaissance). MapCam is a color (four-filter) medium-resolution imager for reconnaissance of the surface of the whole asteroid and searching for plumes and satellites. The wide-angle SamCam is for recording the sample collection process.Learn more (PDF)
  • OSIRIS-REx Laser Altimeter (OLA): Used to create topographic map of the asteroid, both global and at higher resolution around the sample sites. OLA will operate at ranges between 0.5 and 7.5 kilometers from Bennu, OLA is based on a system developed for the US Air Force Research Laboratories XSS-11 mission and on the Phoenix lander Lidar system. Learn more (PDF)
  • OSIRIS-REx Visible and Infrared Spectrometer (OVIRS): an imaging spectrometer sensitive to light with wavelengths from 0.4 to 4.3 microns, for compositional mapping. OVIRS is based on New Horizons LEISA. Learn more (PDF)
  • OSIRIS-REx Thermal Emission Spectrometer (OTES): will map the surface in wavelengths from 5 to 50 microns to map surface mineralogy and study asteroid surface temperatures. It is based on heritage from TES instruments built for Mars Global Surveyor and the Mars Exploration Rovers. Learn more (PDF) and see a photo album.
  • Regolith X-Ray Imaging System (REXIS): A student experiment designed to map elemental abundances on the asteroid's surface. Learn more (PDF)
  • Radio Science: As with all planetary missions, radio scientists will track the spacecraft to measure the mass and gravity field of the asteroid.

Also crucial to the mission is the TAGSAM, the Touch-and-Go Sample Acquisition Mechanism, which will use a puff of nitrogen gas to loosen regolith material from the asteroid's surface, collecting it inside the sampler head. The sample head is the only spacecraft part that is supposed to make contact with the asteroid, so it's not a lander. One scientist likened the sampling method to "high-fiving" the asteroid.

Finally, there are several additional engineering cameras called the Touch-and-Go Camera System or TAGCAMS, which includes a redundant pair of NavCams for spacecraft navigation and a StowCam that will document the storage of the retrieved sample inside the sample return capsule. Learn more.

Best of luck to the mission for a safe launch! Go Atlas! Go Centaur! Go OSIRIS-REx!

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