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3 Pre-Observation Preparations

Advance preparation will enhance the efficiency of your observing run. This includes communicating your program's scheduling requirements and target priorities to the observatory scheduler at the start of the observing episode. Requirements and priorities for subsequent shifts should be revised, if necessary, after completion of your first run. The NASA IUE scheduling policy is included as Appendix B and a pre-observing run check list is provided in Appendix D.

IUE skymaps will be sent to you or to your formally designated Observer at the beginning of the month preceding your scheduled shifts. The skymaps are designed to help you plan your observing session (see Section 3.1). In addition to your program's primary objects, your target list should also include a few alternate targets, to allow you to work around possible spacecraft constraints (Sections 3.2 and 4.4).

Observing a target which is at a large or small angle to the sun may cause the batteries to discharge. If battery discharge is expected during your shift, approval from the Project Scientist prior to arrival at GSFC is normally required. Project policy for spacecraft operations which result in battery discharge is discussed in Section 3.3 and Appendix A. If you should need to add targets to your observing program, contact the Project Scientist prior to arrival at GSFC (see Section 3.4).

Correct 1950 coordinates and field identification are essential. Finding charts are recommended for targets and offset stars fainter than about 6th magnitude (Section 3.5) or for fields where there is another object of comparable brightness within about 15 arc minutes of a bright target.

The presence of fainter stars within the FES's tracking pattern at the target may cause acquisition problems, spectral contamination, or reduced wavelength accuracy. If a target is part of a multiple-star system, is diffuse, or has a visual magnitude below 13.5, an offset maneuver from a nearby star may be necessary (Section 3.6). Special acquisition and observing techniques are used for moving targets (planets, their satellites, asteroids, and comets; see Section 3.7). The orientation of the apertures with respect to the equatorial coordinate system is a function of the spacecraft attitude and time of year. If a particular aperture position angle is required, your observing session can usually be scheduled accordingly (Section 3.8).

The LWP camera is now the long-wavelength camera in general use. The LWR can be used, but it is now configured with a reduced sensitivity to avoid recurrence of a flare in the Ultraviolet Converter section of the detector. The characteristics of the LWP and LWR cameras are compared in Section 3.9.

Several methods of estimating exposure times are discussed in detail in Section 3.10. Even the best-planned program can experience unforseen problems. Section 3.11 summarizes the more common acquisition and observing problems.

Limited amounts of observing time are available for projects which, for scientific reasons, cannot wait until the next IUE observing year. Procedures for applying for this telescope time, referred to as the Project Scientist's Discretionary Observing Time, are described in Section 3.12.

Finally, it is very important that the observatory be informed on a timely basis of your exact observing plans. The annual scheduling of some two hundred programs, along with spacecraft constraints, collaborative programs, and coordination with other telescopes, often results in limited time windows for observing particular objects. Programs are scheduled using information available to the scheduler at the time the monthly schedule is generated, which is ~ 90 days prior to its use.

The GO can take several steps to insure that information available to the scheduler is complete and current. When writing the observing proposal, carefully and completely fill out the required Observation Specification Form. In addition, include any special requirements such as: specific times of the year, partial shifts, collaborative programs, coordination with other telescopes, specific aperture orientations, specific shift sequences, time-critical observations, and high-priority targets.

Shortly after receiving the letter of acceptance for your program, you will be asked to update your original scheduling requests. This information must be provided promptly. When you have a number of shifts scheduled throughout the year, please alert the scheduler to changes in your target priorities. Many scheduling decisions are made at the beginning of the episode. GOs needing time in the first two months of an episode (i.e. June and July) should contact the scheduler as soon as possible after receiving their letters of acceptance. Collaborative NASA/ESA shifts for the entire episode are also scheduled at this time (see Appendix B).

next up previous contents
Next: 3.1 Skymaps Up: IUE OBSERVING GUIDE Previous: 2.4 The IUE Spacecraft

Last updated: 11 June 1997