MSL - Astronomical Observations, Phobos/Deimos, planetary/celestial observations and more |
MSL - Astronomical Observations, Phobos/Deimos, planetary/celestial observations and more |
Jun 29 2013, 05:25 PM
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Senior Member Group: Members Posts: 4247 Joined: 17-January 05 Member No.: 152 |
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Aug 22 2013, 09:04 AM
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Junior Member Group: Members Posts: 22 Joined: 10-August 12 From: Australia Member No.: 6530 |
Quoting Emily: "Point a camera with a 5-degree FOV at a moving speck crossing a moving spot from a rover that was only briefly paused.." This can have been no easy feat! Indeed, how is such precise 'pointing' achieved: gravity provides one vector but Mars (now) has no magnetic field to provide a second. Dean |
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Aug 22 2013, 02:16 PM
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Martian Photographer Group: Members Posts: 352 Joined: 3-March 05 Member No.: 183 |
Indeed, how is such precise 'pointing' achieved: gravity provides one vector but Mars (now) has no magnetic field to provide a second. Sun images show the Sun's position and (optionally) direction of motion in the rover's frame. These allow a full attitude solution or a yaw-only solution. Initial measurement units (gyro-based) update attitude between sun images. MER used a subset of Pancam Sun images. MSL uses Navcam Sun+sky images. The IMU propagates attitude forward, but error builds with drive-time. So the attitude, especially for Sun aims, is precise after a Sun update and before the next drive, and degrades until the next Sun update. The midnight planets page for sol C/369 shows such an update after the drive (and mid-drive imaging). Sol B/3387 shows an update for Opportunity. (In both cases, look for the Sun image/images after "driving...".) |
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