LASCO Calibration Page
The calibrated (Level 1) C2 or C3 image can be generated using REDUCE_LEVEL_1.pro
in the SolarSoft LASCO IDL library. The process is described here.
FITS keywords for the Level 1 product are here
(PDF).
LASCO C3
The official paper (2006) describing all aspects of LASCO C3 calibration is available via SpringerLink.
Photometric Calibration of the LASCO C3 Coronagraph Using Stars by Thernisien et al (2006) also via SpringerLink.
A presentation given by NBR at the LASCO/EIT Consortium Meeting in
May 2001 here (Hypertext).
A paper by Vourlidas and Howard (March 1999) describing the C3 "ramp"
stray light feature (Postscript).
Plots of C3 occulter center: X and
Y
(GIFs). These plots were derived using the procedure FIND_CHORD_CTR.pro.
C3 Vignetting
Note that as of June 2005, final LASCO vignetting functions are available. These vignetting functions are determined to
be the optimal vignetting correction for LASCO C2 and C3 images. No further modifications to LASCO vignetting corrections
are anticipated. These vignetting functions are named as follows and are for the following image types (camera, filters, date range):
- $NRL_LIB/lasco/data/calib/c3vig_preint_final.fts -- C3, Clear/Clear, Pre- June 1998
- $NRL_LIB/lasco/data/calib/c3vig_postint_final.fts -- C3, Clear/Clear, Post- June 1998
- $NRL_LIB/lasco/data/calib/c2vig_final.fts -- C2, Orange/Clear, Entire mission
Further LASCO vignetting information:
-
Overview of various vignetting correction
files at NRL
-
Plots of Rho Leo brightness in C3 using various vignetting corrections
(NBR, March 2001) (Hypertext)
-
Pylon correction derived from 4-week minimum of daily medians and used
to derive C3clearvig_nrl.fts (GIF)
-
Profiles of various vignetting corrections: diagonal
through occulter center (here with
white background), horizontal through
occulter center, perpendicular to pylon(GIFS)
-
Information on NR's attempt to define a C3 vignetting function from
stars in October 2000 (Hypertext).
C3 Stray Light
The high-frequency pattern of stray light in C3 changes noticeably: 1998/11/24 and 2002/06/19.
LASCO C2
A paper by A.Llebaria et al on characterizing C2 photometry, vignetting, stray light, and distortion is available from SPIE Proceedings.
Plots of C2 occulter center from FIND_CHORD_CTR.pro: X
and
Y (GIFs)
C2 Vignetting
Plots of Rho Leo brightness in C2 (from Doug
Biesecker): East limb pixels
or Rsun, West
limb pixels or Rsun (GIFS)
C2 Stray Light
The high-frequency pattern of stray light in C2 changes noticeably three times during the mission: 1998/10/13, 2000/12/02, 2002/02/06.
LASCO C1
Go here.
Updated 2012-11-06 by NR
