Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/documents/dhb/webvol2/c16_hspcalib.fm3.html
Дата изменения: Tue Feb 10 20:06:00 1998
Дата индексирования: Sat Dec 22 17:01:05 2007
Кодировка:
Поисковые слова: п п п п п п п п п п п п п п п п п п п п п п п р п р п
[Top] [Prev] [Next] [Bottom]

41.3 Calibration Algorithms

 Here we describe the algorithms used for each of the calibration steps:

41.3.1 Correcting for Dead Time

 The raw counts need to be converted into count rate. The following equation is used to find the count rate.

x = (raw counts / sample time)

Where x is the observed count rate.

The following equation is used to correct for dead time.

y = x / (1 - x t)

Where:

41.3.2 Computing the True Count Rate

 True count rates for digital data are corrected by using the first equation for a point source and the second for an extended source.

a = (y - pre_amp - darkrate) / (highvolt x pt_effic)

Where:

41.3.3 Computing the True Photocurrents

 True photocurrents (count rates for analog data) are corrected by the first equation for point sources and the second equation for extended sources.

Where:

41.3.4 Calculating Sample Time

 The following equation is used to calculate the sample time. The sample time can be found in the data headers under the keyword SAMPTIME.

41.3.5 Calibration Parameter Polynomial

The HSP calibration parameters listed in Table 41.2 are calculated using the following polynomials.

X = X0 * [1.0 + a01 * (t - t0) + a02 * (t - t0)2 + a03 * (t - t0)3]

+ [a10 + a11 * (t - t0) + a12 * (t - t0)2 + a13 * (t - t0)3] * (T - T0)

+ [a20 + a21 * (t - t0) + a22 * (t - t0)2 + a23 * (t - t0)3] * (T - T0)2

+ [a30 + a31 * (t - t0) + a32 * (t - t0)2 + a33 * (t - t0)3] * (T - T0)3

Where:


[Top] [Prev] [Next] [Bottom]

stevens@stsci.edu
Copyright © 1997, Association of Universities for Research in Astronomy. All rights reserved. Last updated: 01/14/98 16:00:43