6 research outputs found
An Instrument Anomaly in the Mars Exploration Rover Panoramic Camera (Pancam) 1009 nm Filter (R7): Characterisation, Simulation, Correction and Preliminary Verification
During preâflight calibration of the panoramic camera (Pancam) instrument on board the Mars Exploration Rovers MER A (Spirit) and MER B (Opportunity), a discrepancy was noted between 11âband spectra extracted from Pancam images of the camera's radiometric calibration target and reflectance spectra obtained with a spectrometer. This discrepancy was observed in the longestâwavelength filter of the camera (the longpass R7 filter with system λ_(eff) = 1,009 nm) and consisted of a reduction in contrast between bright and dark regions. Here we describe and characterize this effect. We propose that the effect arises because longâwavelength photons close to the silicon bandâgap at 1,100 nm are allowed through the R7 filter, pass through the bulk chargeâcoupled device, scatter from the backside, pass through the chargeâcoupled device again, and are registered in a pixel other than the pixel through which they originally entered. Based on this hypothesis we develop a model capable of accurately simulating the effect, and correct for it. We present preliminary results from testing this correction on preflight, as well as inâflight, images. The effect is small, but in some specific cases in small regions of high contrast, the effect is significant. In inâflight images of Martian terrain we observed the signal in dark shadows to be artificially inflated by up to ⌠33% and analysis of earlyâmission calibration target images indicated that the reduced contrast due to the artifact is equivalent to >100 DN (full well = 4095 DN) for a hypothetical perfectly dark pixel
An Instrument Anomaly in the Mars Exploration Rover Pancam 1,009ânm Filter (R7): Characterization, Simulation, Correction, and Preliminary Verification
During preâflight calibration of the panoramic camera (Pancam) instrument on board the Mars Exploration Rovers MER A (Spirit) and MER B (Opportunity), a discrepancy was noted between 11âband spectra extracted from Pancam images of the camera's radiometric calibration target and reflectance spectra obtained with a spectrometer. This discrepancy was observed in the longestâwavelength filter of the camera (the longpass R7 filter with system λ_(eff) = 1,009 nm) and consisted of a reduction in contrast between bright and dark regions. Here we describe and characterize this effect. We propose that the effect arises because longâwavelength photons close to the silicon bandâgap at 1,100 nm are allowed through the R7 filter, pass through the bulk chargeâcoupled device, scatter from the backside, pass through the chargeâcoupled device again, and are registered in a pixel other than the pixel through which they originally entered. Based on this hypothesis we develop a model capable of accurately simulating the effect, and correct for it. We present preliminary results from testing this correction on preflight, as well as inâflight, images. The effect is small, but in some specific cases in small regions of high contrast, the effect is significant. In inâflight images of Martian terrain we observed the signal in dark shadows to be artificially inflated by up to ⌠33% and analysis of earlyâmission calibration target images indicated that the reduced contrast due to the artifact is equivalent to >100 DN (full well = 4095 DN) for a hypothetical perfectly dark pixel
Data for: A catalogue of unusually long thermonuclear bursts on neutron stars
This data repository for the catalog of unusually long bursts contains the light curves and time-resolved spectral analysis results discussed in the paper. Downloadable plots and the data itself are available. Â Â </p