This guide is intended to convey most of the information a Guest Observer (GO) needs for observing with the International Ultraviolet Explorer (IUE) satellite. This is an updated version of the previous guide (Sonneborn et al. 1987). Several recent developments worth noting are new Beta limits, script format, display pages, FES photometric calibration, skymaps and instrument calibrations. (see Section 3.1, 4.2, 4.3, 4.7 and 5.3 respectively). We urge all IUE GOs, novice and veteran, to make use of this guide.
The Guest Observer will be aided in using the IUE by a Resident Astronomer and Telescope Operator who are responsible for implementing the GO's observational requirements. The constraints and capabilities of the IUE System are constantly evolving. The Resident Astronomer can provide the latest up-to-date information on all aspects of IUE observing capabilities and instrument performance and calibration.
In several respects, observing with the IUE is similar to using ground-based optical telescopes to obtain spectra on photographic plates. All of the activities of the instrument are initiated by real-time commands. The telescope is slewed to the epoch 1950.0 coordinates of the target. The slewing error is typically 3 arc minutes, but may be much larger, so that observer-supplied finding charts should be available. The observer identifies the target by inspection of a 10.8-arc-minute-square visual image of the sky on an interactive image display system. The observer specifies the spectrograph and dispersion mode that is desired. The length of the exposure may be altered in real-time but the exposure level cannot be sampled without reading out the image. As with developing a photographic plate, however, reading the image prevents any subsequent signal from being added to that spectrum. The observer may conduct quick-look analysis at the observing console as soon as 15 minutes after completion of the exposure.
There are some aspects of IUE observing that may be unfamiliar to the new user. Van-Allen-belt radiation may limit the length of the exposures that can be obtained during the second half of the 16-hour NASA operation shift (US2). As seen from the spacecraft, the Earth will appear to circle the sky once every 24 hours, no doubt covering the desired target at just the wrong time. These and other problems will be discussed further below.
IUE Guest Observers can make the most efficient use of allocated observing time through adequate preparation and awareness of potential pitfalls. A brief description of the instrument is given in Section 2. Recommended preparations prior to the observing run are discussed in Section 3 and a pre-observing run checklist is included in Appendix D. GO activities during observing shifts and other important information is given in Sections 4 and 5.
Articles reporting on spacecraft status, changes in observing activities or policies, image processing, data analysis, and so forth are published in the NASA IUE Newsletter. Guest Observers may keep up-to-date on IUE-related matters through the Newsletters. The IUE Image Processing Manual (Version 2.0; Turnrose and Thompson 1984) contains details of the standard image processing performed by the Observatory before it is given to the GO. Information about subsequent IUE image processing, calibration, data reduction, and the Regional Data Analysis Facilities (RDAF) is presented in the IUE Data Analysis Guide (Grady and Taylor 1989). Current IUE addresses and phone numbers are listed in Section 5.4.