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).

Attitude and Time Correction

Exposure Duration Correction

Filter Spectral Data

CCD Quantum Efficiency Information

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).

It gives the status of C3 calibration at that time. The original GIF images used in the presentation are here.

• 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.

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Updated 2012-11-06 by NR