Investigating Geocoronal Absorption for Wavelength Calibration of
Sounding Rockets
Abstract
Due to the high spectral resolution goals (R > 2x10^4)
for the upcoming Full-sun Ultraviolet Rocket Spectrograph (FURST),
instrument calibration will be particularly important. The Solar Physics
groups at NASA MSFC and Montana State University (MSU) have been
developing the tools necessary to achieve this goal. These include
improved tracking of error propagation, in-situ monitoring of the camera
gain with a radioactive Fe-55 source, and even better wavelength
calibration. This presentation will focus on the latter. We will
highlight the development of a calibration method which uses a
two-dimensional second-order polynomial to map pixels to wavelength
under a simulated noisy diagnostic lamp signal. Additionally, we have
introduced a tilted CCD in order to overcome the Nyquist limit. With
this as the background, we have been investigating an effect known well
among ground-based imaging: geocoronal absorption. We have been looking
into how much this effect will be present in the atmosphere at
sounding-rocket altitudes (~100-200km). Many studies
have found ways to correct for these so-called “Telluric” lines.
However, it may be that these lines can in fact be a useful tool to
further improve our calibration, rather than simply a nuisance to be
corrected for!