2009 flights affected by varying offset
|Reported by:||benj||Owned by:||benj|
|Cc:||jatt, mggr, mark1||Other processors:|
VOCALS 2008 flights 7-14 all have a small offset between Eagle and Hawk. Appears to be a boresight offset but is not consistent between flight days (or even between flight lines).
Coincidentally, Specim were asked to perform a calibration on the Eagle and Hawk after return from Chile, and they found an offset in the Eagle that appeared to have been caused by an external shock (though they couldn't say when it had occurred).
Email from Markku Koskela to Phil Goy below (edited 21/Sept/2009 per Specim's request to remove direct quotes - a summary has been inserted instead)
- a spectral and spatial tilt was found in the Eagle sensor
- the corner of the sensor looked like it had been impacted or stressed
- a recalibration was performed and showed a 0.5nm difference at the edges of the image (+/- 0.25nm max change)
- other damage noted was that the Hawk data cable pins were bent (replaced) and the power supplies / computers were loose and moving freely (fortunately no damage occurred).
Working hypothesis at the moment is that the sensor casing received a jolt between data collection for flight days 6 and 7 (hard landing, something bashed it, whatever) that jolted the Eagle slightly loose. This resulted in it moving around slightly (and slowly, or possibly only on hard turns such as between flightlines) during flight. Since the movement was only fractions of a degree, this was not detectable until the data was geocorrected.