DRM Reduction of Mid IR Data

Data from COMICS, VISIR, and MIRSI (and its predecessors) all have slightly different workflows, this page explains some general principals.

Preprocessing

Start DRM at the command line with idl drm_new
Using the Get Files icon, load all the reduced images into the Files window.
Go to Select > Select All to move into the Selections window.
To preprocess the data (i.e. separate into targets and wavelengths) use Programs -> Preprocessing -> All Selected.
This only has to be performed once, so if you see wavelength directories have already been defined, then don't redo it!
It's best to now quit out of DRM, restart it, then navigate to the 'working files' in each wavelength directory (these will now be preceded by a w.

Despiking means we take a look at a region surrounding each pixel, and replace that pixel with a mean value if the pixel value exceeds N sigma of the mean. For VISIR, we typically despike twice with a sigma of 5.0.
This is an optional step, as some degree of despiking may have occurred before using DRM.
We can despike multiple images using Edit -> Expression -> Despike All Selected (changing the value from 5.0 if necessary).
Occasionally one or two additional despikings are necessary to account for excessive pixel response.

To assign latitudes, longitudes and emission angles to the data, we must fit the planetary limb and store the resulting geometry values in the header. This should be done irrespective of whether geometry was assigned during the coaddition stages.
Double-click on the file you wish to navigate, which opens a new Image Tool Window.
Start the process from Programs -> Geometry -> Fit Limb. Use the arrows to the make the planetary silhouette fit the apparent disk (changing the platescale and varying the step size may help in this regard).
If it complains about not being able to find DISTOBJ, this means that the file was not fully preprocessed, you may be using the wrong versions.
When complete, click 'Done, No Optimize.'
Use the Save icon in the top right corner.

Having successfully reduced the data, project the positive image into a cylindrical map ("cylmap") allowing for ease of visualisation and ready inter-comparison with other products.
Within the new Image Tool window: Programs -> Cylindrical Map -> Cylmap of image tool.
Use 2x - 1.0 degree res for MIRSI, 4x 0.5 degree res for COMICS and VISIR.
Select cylmap and mu as the product to be output.
A new image tool opens with the cylindrical map.
File -> Save cylmap -> Yes.
NOTE: the mu-map is the emission angle calculated from the derived longitudes, while mu0 and vdop are the solar incidence angle and the doppler velocity, respectively.

The cylindrical map must have been saved prior to attempting the absolute calibration, using File -> Save cylmap -> Yes.
The final step in the processing of ground-based astronomical images is the assignment of realistic radiance values, as if the data were measured by an ideal detector above the atmosphere.
In the Image Tool Window for the cylindrical map: Programs -> Calibration -> Absolute Calibration
You will then be prompted whether to accept the least-squares fit (weighted according to the date). Unless the fit is very good, this should not be used as the absolute calibration scale factor, and a manual fit should be pursued.
Due to systematic variations in the zonally averaged radiances at high emission angle (that is to say, at high latitude), robust results are obtained by fitting as best as possible the measured intensities to the radiances at low latitudes, near the Equator.
Change the fit manually by entering new values (near to the least squares value) at the prompt.
When satisfied, enter '-1' at the prompt.
When finished, cal_######.cmap.gz, cal_######.gz and cal_######.mu.gz will automatically be generated.