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| QC PLOTS |
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CURRENT |
HISTORY |
| Transmission |
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| number of counts |
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| QC1 database (advanced users):
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plot
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Click on CURRENT to see the current trending (Health Check).
Click on HISTORY to see the historical evolution of the trending. |
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Spectral Transmission |
MIDI has 2 dispersive elements a prism (R=30) and a grism (R=230). The transmission of each element is measured through narrow-band filters at three wavelengths (9.00, 10.46 and 12.80 microns). Measurement through the same filters but without the dispersion are also performed to normalize the transmission.
Procedure:
Observations are made by looking at a blackscreen (blackbody) with the slit.
6 measurements are made. Files 1,2,3 are Photometry (Imaging) with filters and files 4,5,6 are Spectroscopy (prism or grism) with filters (ArIII, NeII, SIV)
Each observation sequence is analysed independently. Saturation and noise limits are verified to guarantee the validity of the results.
On the imaging observation, the position of the beam (x1,y1,dx1,dy1) and the photometry (integral number of counts, P1) is measured for each filter.
In addition, for an exposure time (T1), the maximum count level (m1) are being recorded. The background is removed from a region around the beam.
On the spectroscopy observations, the position y1 of the spectrum
and extension should be the same as in the imaging mode. The background
is removed from a region below and above the spectrum. A 1D fit
is performed along each column to subtract the background.
The signal is integrated over the full spectrum, yielding an integral
number of counts (P2), In addition the exposure time (t2), the maximum
count level (m2) are being recorded.
For each set up we obtain: P(file) = count / exposureTime.
The transmission of a given dispersive element is calculated : #(counts dispersive element)/#(counts open mode)
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QC1 parameters
| parameter |
QC1 database: table, name |
procedure |
| transmission, number of counts |
midi_dettrn, imagex_filter and imagex_number_counts, dispx_filter and dispx_transmission |
- Find the coordinates of the target and of the background
- Collapse each frame of files containing the target with background removed
- For each set up we obtain: P(file) = count / exposureTime
- The transmission of a given dispersive element is calculated : #(counts dispersive element)/#(counts open mode)
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In addition to the above mentionned QC1 parameters, the position of the image (X, Y) and the size (dx, dy) are archived as well.
Trending
Strong variations in transmission are usually due to pressure problems.
History
2011-09-10: intervention to detect and fix vacuum leaks.
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