The observation target for the mission was the coronal hole at the solar north pole. During the prime mission, the 900" long slit was moved over the surface of the sun to obtain a 10" wide raster with 2" steps. The slit was positioned nearly radially with 100" above the northern limb of the sun. A wide range of exposures were taken to observe a wide variety of bright and faint lines. A series of spectroheliograph and Halpha images were taken of the spectrograph slit jaws to reference the slit location. Final image coregistration will be accomplished using slit jaw, Tmin continuum images and Kitt Peak/MDI magnetograms. An excellent collaborative data set was obtained at Kitt Peak Observatory (chromospheric and photospheric magnetograms), Big Bear Solar Observatory and University of Hawaii. The space based collaborative observing campaign included SXT (YOHKOH), MDI (SOHO), EIT (SOHO), CDS (SOHO) and SUMER (SOHO). The slit spectra show an interesting collection of explosive events in C IV. The spectroheliograph images show C IV loop like structures near the limb.
The flight also was the first scientific flight of the new digital attitude control system produced by the Lockheed Martin SPARCS group at the White Sands Missile Range. The system utilizes fast, programmable digital control of the payload. The previous problem of ground loop noise on the shielded sensor lines was entirely eliminated by the incorporation of a fiber optic sensor data line. The performance of this new system was superb. Acquisition occurred within 30 seconds of opening the aperture door. The noise on the sensor output lines was 0.05 arc-seconds. The stability over the entire flight was 1.5 arc-seconds peak to peak. The stability of the pointing over a typical 10 second exposure was 0.2 arc-seconds peak to peak and <0.1 arc-seconds peak to peak for a typical 1 second exposure. This pointing stability in future flights will enable very high spatial resolution solar images to be obtained from a sounding rocket platform.
A set of sample images from the flight are given below. These were produced by electronically scanning positives produced from the flight film. The limb is placed in the top of the pictures; the slit orientation is up and down. Three fidicual wires (225 arc-seconds apart) are visible in the spectra and slit jaw images. The slit width is 0.5 arc-seconds in scale and the fiducial wire spatial width is are 2" arc-seconds. The images are scaled with darker areas corresponding to higher intensity.
The above two images are sample spectra taken during the first raster step of the flight. The wavelength range of the spectra presented is 1500-1700 Angstroms. The spatial resolution is <1 arc-second along the slit. The limb is located at the top of the spectra; wavelength increases left to right. The C IV doublet (1550A), the He II emission line (1640A), the C I multiplet (1660A) and the Al II emission line (1670A) are all clearly present. A variety of turbulent and Doppler shifted explosive events are present in the slit spectra. Limb brightening is clearly present in the emission lines.
The above images show the C IV and Lyman alpha spectra taken during
the first step of the HRTS 10 raster. The limb is located at the top of the
spectra.
The above two images were taken with the spectroheliograph focal plane
instrument. The spectoheliograph isolates a 20 Angstrom bandpass of the UV
continuum at selected wavelengths and produces an image of the spectrograph
reflective slit jaws. The slit and three fiducial wires are clearly seen. Th
e
image was taken in the 1560A bandpass of the instrument. Loop like
transition region/chromosphere structures are visible particularly near the
poles.
The above two images were taken with the Halpha slit jaw monitoring
system. Two 60mm mica etalons are utilized to filter the incoming solar
radiation and produce a high spectral purity 0.5Angstrom Halpha image. The
system also feeds an onboard video camera system which is utilized to point an
d
focus the payload during flight. The Halpha images are also used for
coregistration of the spectra with ground and space based solar observatories.