DAS40 - New and Updated Features

D. Phillips and S. Giordano


This document describes the new and updated features of the UVCS Data Display and Analysis Software (DAS). They include calibration updates as well as those for functional, data handling and aesthetic features. 

Calibration updates include a new calibration scheme that allows for changing calibration over time: the DAS automatically chooses the calibration files nearest to the selected observation in time, and interpolates (where appropriate) to obtain the calibration parameters.  In the case of effectively one-time changes, such as those due to thermal reconfiguration, the DAS simply uses the new calibration for succeeding dates.  If a data file is newer than the most recent calibration file, no extrapolation is attempted, and the calibration parameters of the most recent calibration file are used.  The user should be able to keep up with the latest calibration by downloading new calibration files from the UVCS web site, without having to update the DAS itself.

So far the only time-dependent calibrations performed are for the mirror height function and for the efficiencies of the three spectral channels, but other time-dependent effects can be incorporated easily using modified calibration files.

Radiometric Efficiency:
UVCS OVI channel radiometric efficiency vs. time DAS 33 and earlier used the laboratory calibration, represented by the solid line in the graph.  DAS 40 takes into account the reduced system efficiency over time as a function of aperture, and linearly interpolates in time between the curves marked above.

Note that at small apertures there is a large reduction in efficiency, but the change becomes negligible at very large apertures. Also, for the OVI channel, the 2005 data fits equally well to the 2004 calibration curve.

UVCS Redundant LYA channel radiometric efficiency vs. time UVCS LYA direct channel radiometric efficiency vs. time For the LyA direct channel, there are also differing efficiencies for different wavelength bands owing to transmission qualities of the optical system. The laboratory and early-mission curve is for wavelengths near LyA (1216 - 1250 Angstroms), with efficiencies dropping at higher and lower wavelengths. The Aug. 2005 observations indicate an additional 10-20% degradation of efficiency at these higher and lower wavelengths, compared to the LyA baseline. These wavelength-dependent efficiency changes over time have also been incorporated into the calibration files for the DAS.

Mirror Pointing Calibration:

DAS33 and 40 mirror comparison
Solid line is DAS33 release, dashed is DAS40 calibration for data before thermal reconfiguration at the end of 2003, and dotted is the calibration for mirror height after the reconfiguration. 
The pre-reconfiguration curve is nearly identical to the DAS33 calibration, with the exception of high heights and low ones.  Note that the DAS33 mirror calibration did not fully cover the lowest heights (below 1.74R);  DAS40 calibrations cover these low heights, so that the "command mirror", which referred to the laboratory mirror calibration, is now generally obsolete.
Pointing calibration has also been slightly updated to include departures from sun center owing to the imperfect circularity of the UVCS roll ring. These departures are generally less than 10 arcsec.
In addition, the DAS treats SOHO spacecraft roll (either 0 or 180 degrees) consistently throughout. For example, the graphical pointing display displays proper sun pointing. Note that INS_ROLL still describes only the instrument roll; please add SC_ROLL field to obtain actual sun coordinates.
Other calibration improvements include better VLD calibration and a mirror/gratings X-talk correction using ancillary data files.

This work addresses some open actions presented on the UVCS web page
http://cfa-www.harvard.edu/uvcs/get_involved/future_release.html  reported here below.
The red tasks have been fixed in the DAS version here presented.

The list below represents ongoing work to the Data Analysis Software (DAS).

Provide time variation in efficiency of the OVI direct channel
Provide changed mirror calibrations over time to reflect changes from thermal reconfiguration
Provide time variation in efficiency for OVI redundant and LYA channels if appropriate
Provide time variation of wavelength calibration
Provide telescope mirror and grating cross talk correction
Improve precision of pointing calibration below 1.74 R_sun. This provides a value at 1.5 R_sun and allows consistency in displaying the height throughout the DAS
Provide estimate of second order radiometric calibration
Provide improved stray light characterization
Improve consistency of conversion from arcsec to solar radius from the spacecraft for the DAS and the extension code
Provide White Light Channel characterization and calibration
Provide filter transmission information (automatic radiometric calibration for disk observations)
Improve precision of pointing variation with roll (small effect)
Provide dark count files
Provide instrument spectral line profile function

The package consists of the following files:

DAS40/DPS/ das40.pro Main code

ext40.pro Extension code

search_catalog_1.3.pro Search catalog code

das.help Help file

das.pro batch file to run the code

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DAS40/CAL/ D.40.1996.01.02, etc. Calibration files

xtalk_LYA.tab LYA grating positions for X-talk correction
(Up to date files at )

xtalk_OVI.tab OVI grating positions for X-talk correction
(Up to date files at )

stray_light_vld_fit1.dat VLC stray light
This files and more
DAS40/TABLES cat_sg_YYYY_A.tab
Tables A and B for Observation catalog,
created from FITS file headers.
Presently a file for each year (YYYY) from 1996 to 2001

UVCS Observed CMEs list
from J.Raymond and A. Ciaravella,
last update Oct 23, 2003

UVCS Observed Comets list
from J.Raymond and S. Giordano
last update May 20, 2004

In addition to the code:

1 - if you want display colored buttons, you should add the following lines somewhere in your ".Xdefaults" file (in the top level of your home directory):
! IDL colors
Idl*background:         LightBlue
Idl*foreground:         Black
Idl*white*background:   White
Idl*green*background:   Green
Idl*yellow*background:  Yellow
Idl*blue*background:    Blue
Idl*lblue*background:   LightBlue
Idl*red*background:     Red
Idl*magenta*background: Magenta
Idl*cyan*background:    Cyan
Idl*azure*background:   Azure       
Idl*aqua*background:    Aquamarine   
Idl*gold*background:    Gold       
Idl*indian*background:  IndianRed   

2 - to manage DAS under 24-bit Linux displays add also the following lines in your ".Xdefaults" file
Idl.gr_visual: TrueColor

To run the DAS40 code:
  1. change to the directory DAS40/DPS/
  2. start IDL
  3. compile the code from the IDL prompt type: "@das {Return}"
  4. bring up the DAS software interface by typing "mn {Return}"
The updated and new features are organized and described in this document
following the menus and buttons as they appear in the DAS main window.


Main Window

General Menu

SPVL Data Menu

Calibration Menu

IMAGE Data Menu


The DAS comes with up-to-date catalog tables as of the date you downloaded it. If you would like the newest tables, please check http:cfa-www.harvard.edu/uvcs/get_involved/download.html

Display Data

Quick Look

Display 2D Images

Display Pointing