Space Topics: Mars Reconnaissance Orbiter
The Year in Pictures: 2008
Falling Toward Mars
Credit: NASA / JPL / U. Arizona |
Two feats of spacecraft navigation and control combined to create this awesome
action shot of Phoenix falling to its
landing on Mars. The Phoenix
polar lander was nearing the end of its 679-million-kilometer (422-million-mile) journey
to Mars. It had completed the fiery entry period of its landing, jettisoned
its heat shield, and deployed its parachute.
At the same time, Mars
Reconnaissance Orbiter was flying on its own path
around Mars. The photo, captured by the High Resolution Imaging Science
Experiment (HiRISE) camera, was designed to capture an image of Phoenix
that might help engineers figure out the cause of a failure of Phoenix
upon landing, so the orbiter was programmed to spin as the image was taken
to compensate for Phoenix’s apparent motion and produce a sharp image
of the spacecraft. With the fast relative speeds of Phoenix along with
the orbiter, and the uncertainty in Phoenix’s exact position that
arose from uncertainties about how long its entry would take, the HiRISE
team predicted only a 20 percent chance of successfully capturing an image
of Phoenix in flight. (More detail on how this image was captured is reported
in The Planetary Society Blog.)
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Phoenix landing
HiRISE took this photo of Phoenix under its parachute as it descended toward Mars on May 25, 2008.
Credit: NASA / JPL / UA
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Both the imaging attempt and the landing were successful, so the image
was not needed for engineering, but it provided an amazing snapshot of
a spacecraft in the act of landing on another planet. HiRISE is so sharp
an imager that you can even make out the stripes on the parachute and the
shroud lines connecting it to the lander. Initially, analysts focused only
on Phoenix. But upon further investigation of their image, the HiRISE team
realized that the background view was impressive, too: a 10-kilometer crater
named Heimdall, on whose ejecta blanket Phoenix now sits. (Although it
appears that Phoenix was falling into the crater, that’s an optical
illusion. The view is oblique, and Phoenix was much closer to the orbiter
than was the crater.) Later, the team
realized that the blackened heat shield of Phoenix is also visible in the
image as a black dot falling toward Mars on a trajectory similar to the
bright spacecraft.
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Phoenix lander, parachute, and heat shield
As Phoenix descended, HiRISE captured a photo of the lander, its parachute, and the blackened heatshield that slowed Phoenix' entry into Mars' atmosphere, recently detached and falling ahead of the spacecraft.
Credit: NASA / JPL / UA
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