Ultraviolet Spectral Atlas of a Sunspot from 1978 Rocket Flight

HRTS II rocket flight data from 1978 provides 4.2 minutes of ultraviolet spectra (1190-1730 Å) for a sunspot with 2 arcsec spatial resolution. The atlas includes spectra from three sunspot areas, an active region, and a quiet region, processed from photographic film. U.S. Naval Research Laboratory scientists built the High Resolution Telescope and Spectrograph instrument used to collect this data.

Use Cases

• Analyze transition region line profiles to study downflowing gas velocities above sunspots, accurate to 2 km/s.
• Compare absolute calibrated solar intensity across sunspot, light bridge, active region, and quiet region spectra.
• Investigate continuum radiation enhancement and unique line appearances within the sunspot light bridge feature.
• Study spectral and spatial evolution over the 0.2-20.2 sec time resolution across the radially oriented slit path.

Strengths

• High spectral and spatial resolution with 2 arcsec spatial sampling and wavelength coverage from 1190 to 1730 Å.
• Absolute intensity calibration with an accuracy within 30% (rms) and velocity measurements accurate to 2 km/s.
• Data covers multiple solar features: three sunspot areas, an active region, and a quiet region for comparison.

Limitations

• Single observational event from a 4.2-minute rocket flight on 13 February 1978, limiting temporal coverage.
• Absolute intensities are relative to an average chromospheric velocity, not an absolute solar rest frame.
• Original data captured on photographic film, introducing potential analog processing artifacts.

Provenance

Source

High Resolution Telescope and Spectrograph (HRTS) instrument built at the U.S. Naval Research Laboratory.

Collection Method

Spectrograms recorded on photographic film during a Black Brant VC rocket flight, later digitized via microphotometry at the Institute of Theoretical Astrophysics in Oslo.

Time Range

1978-02-13 (4.2 minutes of observation during the rocket flight).

Freshness

1978-02-14

Geography

Observations target solar active region McMath 15139, from disc center through a sunspot to the solar limb.