Skylab: A Progress Report

The Skylab Apollo Telescope Mount contains six principal instruments spanning the X-ray to visible wavelength range. These experiments include an externally occulted white light coronagraph from the High Altitude Observatory which observes the outer solar corona from 1.5 to 6.0 radii from Sun center, in broadband (3500–7000 Å) white light with approximately 10″ spatial resolution. An X-ray spectrographic telescope of the American Science and Engineering, Inc. employs six filters and an objective grating to observe a 48′ field of view in the wavelength range 3.5–6.0 Å, with approximately 3″ spatial resolution. A scanning ultraviolet polychromator, spectroheliometer of the Harvard College Observatory is capable of observing 1.2 Å spectral resolution from 300–1350 Å with a 7 detector array. The field of view of the instrument is determined by its operational mode and ranges from 5′ × 5′ to 5″ × 5″. An X-ray telescope from the Marshall Space Flight Center employs five metal filters to observe the 5–33 Å spectral region with 2.5″ spatial resolution over the 40′ field of view. The Naval Research Laboratory has supplied two instruments: the first, an XUV spectroheliograph, covers wavelength regions 150–335 Å and 321–625 Å, with somewhat better than 5″ spatial resolution and a spectral resolution of 0.13 Å (for a 10″ feature). The second instrument, a slit spectrograph, covers the spectral range 970–3940 Å in two bands, 970–1970 and 1940–3940, and has 0.5 and 0.1 Å spectral resolution respectively, with a 2″ × 60″ slit. Additionally, these principal experiments are supported by two Hα telescopes and a broadband (150–600 Å) ultraviolet monitor for astronaut use. All experiments except that of the Harvard College Observatory (which utilizes photoelectric detectors) employ film to be recovered and installed during astronaut extravehicular activity. Operating in concert in a joint observing program designed to obtain observations of certain solar phenomena, the experiments have now completed more than two months of manned operation and, in the case of the AS&E, HCO and HAO instruments, approximately two additional months of unmanned operations. Representative preliminary results are outlined from several of the experiments below.