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Emily Lakdawalla • Sep 29, 2016

OSIRIS-REx’s cameras see first light

As OSIRIS-REx speeds away from Earth, it’s been turning on and testing out its various engineering functions and science instruments. My favorite proof of a happy instrument is data, especially camera data, so I’ve really been enjoying the series of “first light” images that OSIRIS-REx has been sharing over the past few weeks.

The first such image was this one, from the star tracker. Star trackers help a spacecraft understand its orientation in space, by shooting photos of the stellar background and comparing them to an onboard star catalog. With help from astrometry.net I can tell you that this particular bit of the sky lies deep in the southern hemisphere and includes Beta and Gamma Sculptoris.

First light for OSIRIS-REx's star tracker
First light for OSIRIS-REx's star tracker Taken September 12, 2016.Image: NASA

Next we heard from all the science instruments, with visual evidence of fine performance from MapCam and PolyCam, two of the cameras within the OCAMS instrument suite. The three OCAMS cameras each have different fields of view; SamCam has the widest view, then MapCam has a view roughly 5 times narrower (and 5 times higher-resolution), and PolyCam’s view is another 5 times narrower and more detailed. The image below is from the middle-resolution MapCam, and shows a bit of the sky in Taurus. Astrometry.net had a harder time matching this one, presumably because of the wide view and hot pixels. These cameras are intended for much brighter targets (i.e. a nearby asteroid) so produce images that are a bit noisier when they’re used to image fainter sources like stars.

First light for OSIRIS-REx MapCam
First light for OSIRIS-REx MapCam On Sept. 19, the OCAMS MapCam camera recorded a star field in Taurus, north of the top of the constellation Orion as part of the OSIRIS-REx spacecraft’s post-launch aliveness test. MapCam’s first color image is a composite of three of its four color filters, roughly corresponding to blue, green, and red wavelengths. The three images are processed to remove noise, co-registered, and enhanced to emphasize dimmer stars.Image: NASA / GSFC / University of Arizona

Finally, here’s my favorite image from the bunch. It was taken by StowCam, one of three cameras added to OSIRIS-REx for navigation and engineering purposes. StowCam is for documenting the process of transferring the sample canister to the sample return capsule, and as you can see it’s doing a great job of showing us how the sample return capsule looks!

First light for OSIRIS-REx StowCam
First light for OSIRIS-REx StowCam On September 22, 2016, two weeks after launch, the OSIRIS-REx spacecraft switched on the Touch and Go Camera System (TAGCAMS) to demonstrate proper operation in space. This image of the spacecraft was captured by the StowCam portion of the system when it was 6.17 million kilometers away from Earth and traveling at a speed of 30 kilometers per second around the Sun. Visible in the lower left hand side of the image is the radiator and sun shade for another instrument (SamCam) onboard the spacecraft. Featured prominently in the center of the image is the Sample Return Capsule (SRC), showing that our asteroid sample’s ride back to Earth in 2023 is in perfect condition. In the upper left and upper right portions of the image are views of deep space. No stars are visible due to the bright illumination provided by the sun.Image: NASA / MSSS / UA

Here’s a diagram to help you understand the geometry of StowCam’s point of view:

Locations of the OSIRIS-REx TAGCAMS camera heads
Locations of the OSIRIS-REx TAGCAMS camera heads The Touch-and-Go Camera System (TAGCAMS) consists of three wide-field camera heads and a digital video recorder (DVR). Two of the cameras, the NavCams, will image the asteroid Bennu and background stars as the spacecraft nears the asteroid, to support optical navigation of the spacecraft relative to the asteroid. The third camera, StowCam, will image the transfer of the sample collected from Bennu's surface from the sample collector to the Earth-return sample capsule.Image: MSSS

Congratulations to the OSIRIS-REx team on the successful operation of their sensors and science instruments! I can’t wait for next year’s Earth flyby, when we’ll get to see them tested out on nearby targets.

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