Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://www.stsci.edu/documents/dhb/webvol2/c08_fosdataanal.fm6.html
Дата изменения: Tue Feb 10 20:05:48 1998 Дата индексирования: Sat Dec 22 18:49:34 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 п п п п п |
We recommend running deaccum with all of your ACCUM mode .c1h files. It will also work with statistical error (.c2h) files and correctly unbundles these data in quadrature. This task will not work for data files that contain wavelengths (.c0h) or data quality values (.q0h or .cqh files). The group parameter EXPOSURE is updated in the output image headers to reflect the change in exposure time associated with each data group. For example, to unstack the calibrated flux data in the image y3ci0203t.c1h, and write the results to the new image y3ci0203u.c1h, use the command:
fo> deaccum y3ci0203t.c1h y3ci0203u.c1h
Since the calfos (pre-onboard) GIM correction is applied on an integral pixel basis in the x-direction only, uncorrected motions of up to +/- 0.5 pixels can occur in X. This effect is much smaller for observations corrected by the onboard GIM correction. For observations obtained prior to the implementation of the onboard GIM correction (the presence of header keyword YFGIMPEN set to "T" tells you if the onboard correction has been performed), the actual decimal magnitude of GIM motion can be evaluated with STSDAS task gimpcor. This information can be useful for evaluation of the GIM-related uncertainties in observing modes to which the correction is not applied, as well, such as pre-onboard GIM-correction spectropolarimetry and IMAGE mode.
This task calculates the x-direction GIM correction in fractional diodes predicted by the FOS GIM model. Rounding of the output to the nearest integer gives the actual correction that would have been applied by calfos in normal pipeline processing if the OFF_CORR switch were enabled.
The size of the y-motion, which is important for the evaluation of photometric losses, is also calculated. Recall that no GIM correction is made in the y-direction prior to the implementation of the onboard GIM correction.
gimpcor is essentially a small version of calfos, but gimpcor does not actually perform any corrections. All inputs required for running calfos are also required for running gimpcor. The image motion corrections are output in diodes, not pixels, for x and Y-base units for y. For example, the following command can be used to show the magnitude of the GIM correction for the observation y0nt0303t (an observation made in RAPID mode, with each line corresponding to each readout of the science diodes). Note that components of the geomagnetic field are also given along the V1, V2, and V3 axes.
fo> gimpcor y0nt0303tY0NT0303T XOFF YOFF B(V1) B(V2) B(V3)
Y0NT0303T 0.7937 -18.9236 -0.144756 -0.252337 -0.187240
Y0NT0303T 0.7774 -22.6758 -0.158107 -0.241623 -0.200176
Y0NT0303T 0.7540 -26.3918 -0.171826 -0.228918 -0.211748
Y0NT0303T 0.7235 -29.9800 -0.185674 -0.214425 -0.221575
....
Y0NT0303T -0.1363 30.6008 -0.142325 -0.105515 0.195814
Y0NT0303T -0.0940 31.9168 -0.134098 -0.119314 0.193947
This example will unwrap the image y20vk10gr.d0h using a threshold value of 20000 and creating an unwrapped image called uw10g.d0h.
fo> unwrap y20vk10gr.d0h uw10g.d0h thresh=20000.
This routine computes the offset of one spectrum from a reference spectrum, as a function of wavelength and diode position in the frame of the reference spectrum. The input spectra may be divided into a number of equally sized bins. Each bin in the target spectrum is cross-correlated with the corresponding bin in the reference spectrum and an offset is determined. The offsets for all bins are placed in an output table as both diode and wavelength offsets.
The following example will compute the offset between upper and lower apertures for the spectra in file h57red. The upper aperture is in the first group of the file and the lower aperture in the second group. The wavelengths for the first group are stored in wh57red (group 1). Results are written to a table called offsets.tab.
fo> waveoffset h57red[1] wh57red[1] h57red[2] tab=offsets