ESA Science & Technology - Publications Archive

The present document describes the mission operations associated with the International Ultraviolet Explorer (IUE) spacecraft in the context of the 18.5 years of orbital operations in the IUE Project which was a collaboration between NASA, ESA and PPARC. In chapter 1 the objectives of the IUE mission, the goals and capabilities of the spacecraft, the payload and the ground segment are described, as well as some examples of the scientific capabilities of the project. The characteristics of the spacecraft, the spacecraft subsystems and the ground observatory control systems are detailed in chapter 2. Chapter 3 lists the main spacecraft events in the course of the 18 years of the duration of the orbital operations. In chapter 4, the IUE orbit and its evolution is described. The most important problems in the spacecraft subsystems are described in Chapter 5 together with the solutions. Special emphasis is given to the different Attitude Control systems associated with the progressive Gyro failures culminating in the One-Gyro control system used during the last six months of orbital operations. In chapter 6, the spacecraft thermal design is described. The three appendixes contain important dates in the area of spacecraft operations:

• Appendix A: Earth shadow seasons
• Appendix B: Orbital corrections (Delta-V's)
• Appendix C: On-Board-Computer malfunctions