Missing exposures and bright exposures - example#

The study PRY_footpoints_HI2 is an interesting test case as it has a large number of wavelength windows (23) and the windows vary significantly in size.

There are 6 problem exposures: numbers 26, 57, 58, 59, 61 and 88.

Extracting the exposure times using the getexp() method yields zero exposure times for exposures 57, 58, 59 and 88, but not 26 and 61.

The table below goes through wavelength window and indicates the problems for the 6 exposures.

Window Detector Size 26 57 58 59 61 88
Fe XI 182.20 SW 32 OK Dark Dark Dark OK Dark
Fe X 184.60 SW 80 OK Dark Dark Dark OK Dark
Fe XII 186.75 SW 40 OK Dark Dark Dark OK Dark
Fe XI 188.40 SW 64 OK Dark Dark Dark OK Dark
Ca XVII 192.82 SW 40 OK Dark Dark Dark OK Dark
Fe XII 195.48 SW 96 OK Dark Dark Dark OK Dark
Fe IX 197.86 SW 24 OK Dark Dark Dark OK Dark
S VIII 198.57 SW 24 OK Dark Dark Dark OK Dark
Fe XIII 202.04 SW 32 OK Dark Dark Dark OK Dark
Fe XIII 203.83 SW 32 OK Dark Dark Dark OK Dark
O V 248.95 LW 64 Bright (W) Dark Dark Dark Bright (W) Dark
Al VIII 250.50 LW 48 Dark Dark Dark Dark Dark Dark
Fe VIII 253.98 LW 40 Dark Dark Dark Dark Dark Dark
He II 257.30 LW 128 Dark Dark Dark Dark Dark Dark
Fe XVI 262.98 LW 24 Dark Dark Dark Dark Dark Dark
S X 264.50 LW 40 Dark Dark Dark Dark Dark Dark
Mg VI 268.99 LW 24 Dark Dark Dark Dark Dark Dark
Fe XIV 274.20 LW 32 Dark Dark Dark Dark Dark Dark
Mg V 276.31 LW 120 Dark Dark Dark Dark Dark Dark
Mg VII 278.39 LW 32 Dark Dark Dark Dark Dark Dark
O IV 279.80 LW 32 Bright (W) Bright (W) Dark Dark Bright (W) Bright (W)
Mg VII 280.75 LW 32 OK Bright Dark Dark OK Bright
Fe XV 284.16 LW 24 OK Bright Dark Dark OK Bright

The descriptors for the pixels are:

OK - normal exposure
Dark - no signal at all in exposure
Bright - exposure is normal but intensities are anomalously bright at every pixel
Bright (W) - exposure is anomalously bright but spectrum is weird

The anomalously bright exposures 57 and 88 for the Mg VII 280.75 and Fe XV 284.16 windows are probably due to the fact that exposure times of 0 have been assigned to these exposures. When the intensity is computed, a division by the exposure time is performed. It seems likely that an arbitrarily small exposure time has been used giving a much higher intensity value than normal. The image below shows an image from the Mg VII 280.75 window, with the two bright exposures clearly seen.

Only two windows show 'weird' spectra. Examples from exposure 26 are shown below:

The left image is from the O V 248.95 window, the right from the O IV 279.80 window. The symmetry of the two spectra is striking. It's also noticeable that the two wavelength windows bracket 9 windows on the LW detector where all 6 exposures are dark. The two LW windows outside of these 'brackets' do not have all 6 exposures missing.

The spectra in the two weird windows have high values for about 75% of the window but then drop to zero. It is not clear if the bright pixels actually contain good data points as the lines in the windows are weak, however I believe they do not contain good data. Note that the magnitude of the spectrum in the two windows is different by a factor of about 2.3. This is close to the difference in effective areas between the two wavelengths (factor of 2.2, with 279.80 being more sensitive).

This particular version was published on 19-Mar-2010 16:18 by PeterYoung.Top