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Volumn 306, Issue 5702, 2004, Pages 1753-1756

Atmospheric imaging results from the Mars exploration rovers: Spirit and opportunity

Author keywords

[No Author keywords available]

Indexed keywords

DUST; IMAGING TECHNIQUES; INFRARED RADIATION; MICROMETERS;

EID: 10044294790     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1104474     Document Type: Article
Times cited : (212)

References (32)
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    • note
    • A martian solar day has a mean period of 24 hours 39 min 35.244 s and is referred to as a sol to distinguish this from a roughly 3% shorter solar day on Earth. Sol 1 was defined to begin at local solar midnight immediately before landing.
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    • note
    • Images were returned primarily in two formats. First, a thumbnail image was down-linked: thumbnails comprise a full-frame image, down-sampled from 1024 by 1024 pixels to 64 by 64 pixels and compressed to 1 bit per pixel. In thumbnail images, the Sun is just over 1 pixel in diameter, although the flux is typically spread over 4 or more pixels. Second, a "SUN" subframe was down-linked with lossless compression. A "SUN" subframe is 63 by 63 pixels, centered on the centroid of the solar disk. Generally, a single observation resulted in both types of images; in some cases, one product exists but the other was not down-linked. Wherever possible, observations with the lossless, full-resolution subframe were used for analysis; thumbnail observations were used only to fill in gaps in the record.
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    • note
    • The sequences used to image the Sun as it drifted across the CCD included sequences requested by the science team, but were primarily "sun-gazes" using L8 images of the Sun to update the rovers' attitude data.
  • 18
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    • note
    • The red leak appears as a small transmission in filter-level tests. However, in later and system-level tests with much worse signal-to-noise ratios, the red leak appeared to contribute more transmitted flux than the principal band pass. The temperature dependence of the system response through the L8 filter is similar to that of a 700- to 800-nm filter. The solar flux versus position data sets were analyzed using all of the left-eye flat fields, under the assumption that atmospheric optical depth did not change during the ∼15-min experiment. The L1 flat field produced the most consistent results, although the L2 (750 nm) flat field was nearly as good. The L7 (430 nm) flat field is markedly different from the L1 or L2 flat fields.
  • 21
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    • note
    • The observed intensity, I, is determined by d[In(I)] = κ(s) sin[κ(s)] ds, where s is the path and κ is the extinction per unit distance, such that τ = ∫κ dz, and z is altitude. For the scale-height case, κ = τ/H exp(-z/H), where H is the scale height. The relation between z, θ, and s is purely a function of the geometry (i.e., the curvature of the limb). An arbitrary vertical profile can be ruled out by these data if it yields values of I that are out of the bounds defined by the scale-height case and its uncertainty.
  • 25
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    • note
    • We used the doubling and adding radiative transfer code of (23). Because of a 7% uncertainty in the absolute radiometric calibration, we chose to model the relative variations in intensity rather than the absolute intensity. After a best-fit model was found, a correction factor for the absolute intensity was derived. The intensity shown in Fig. 2 includes this correction factor. Intensities for the six filters (in increasing wavelength order) are multiplied by 0.97, 1.035, 0.984, 1.004, 1.021, and 0.861 for Spirit and 1.177, 1.155, 1.144, 1.109, 1.114, and 0.962 for Opportunity.
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    • note
    • This work was funded by NASA through the Mars Exploration Rover Project. We thank the MER engineers and scientists who enabled the observations described here.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.