partial aperture solar calibrator PAC or PASC

One of two on-board external solar calibrators on Landsat 7 ETM+. The PASC consists of structure in front of the ETM+ aperture that has four independent pinholes for reflecting solar irradiance on a presumably parallel path to the optical axis of ETM+ as it comes over the North Pole and into sunlight. As compared to FASC measurements, PASC irradiance from a single pinhole at a time only fills a small part of the defining aperture. PASC measurements were made approximately once a day prior to Failure of the Scan-Line-Corrector (SLC), and once every other day subsequently. The SLC-failure also necessitated rewriting the Software for PASC processing by the image Assessment System (IAS) at EROS Data Center in Sioux Falls, SD. Unfortunately, there are two major problems with PASC data: 1) the elliptical PASC images are saturated in several bands, and 2) an as-yet unknown cyclic variation has made them unusable in an absolute sense. The relative Gain or Responsivity of the detectors can be calculated from factors that include, known solar spectral irradiance, measured solar zenith and azimuth angles. Also see full aperture solar calibrator and internal calibrator. (Source: Dr. John Barker)

Sign up for the Timbercon newsletter:

[honeypot website]

By submitting this form, you are consenting to receive marketing emails from: Timbercon, 20245 SW 95th Avenue Tualatin, OR 97062 United States, You can revoke your consent to receive emails at any time by using the SafeUnsubscribe® link, found at the bottom of every email.

This site uses cookies to enhance the user experience, and by browsing this site, you are accepting the receipt of cookies on your browser from this site. To manage use of cookies, please refer to your browser settings. Click here to learn more.