Number 16, July 2001
Contents: 1) Correction to CalFUSE v(HELIO) calculations 2) Release of CalFUSE v2.0 in sight 1) Correction to CalFUSE v(HELIO) calculations Following a careful analysis, the FUSE team at JHU has established that the correction for the Earth's orbital motion has been applied with the wrong sign in the CalFUSE pipeline. This problem affects all CalFUSE versions prior to, and including, v1.8.7. Specifically, the problem originates in an inconsistency between the sign of the file header keyword containing the velocity correction from Geocentric to Heliocentric frames, and the implemented algorithm. The correction from spacecraft to Geocentric frame is done correctly. Note that, although not used by the CalFUSE pipeline, the header keywords for the LSR corrections (V_LSRDYN and V_LSRSTD) are populated using the same sign convention. This inconsistency will be removed in the upcoming (v2.0) release of the CalFUSE pipeline. In the meantime, data processed by CalFUSE, v1.8.7 and earlier can be easily corrected for the error in the application of V_HELIO (from file header): lambda[new] = lambda[old] * ( 1. - 2.*V_HELIO / c ) A full discussion of the problem, investigation and remedies can be found at: 2) Release of CalFUSE v2.0 in sight On a related note, the new, significantly updated, version of the CalFUSE data reduction pipeline, v2.0, is now expected to be released for beta testing in the next few weeks. A general release is expected by September 2001. This version of the calibration pipeline features the following improvements over v1.8.7: - Corrected heliocentric wavelength scale - Detection and removal of event bursts - Walk correction (for low-pulse-height events) - Improved scattered-light model - Astigmatism correction - Optimal (weighted) spectral extraction - Improved wavelength calibration - Improved flux calibration Those FUSE users who wish to participate in the beta testing of v2.0 are encouraged to contact us at fuse_support@pha.jhu.edu
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