Determination of the best calibration for IUE data is an ongoing process. Due to the stability of the cameras, absolute calibrations derived early in the mission are still in use. During the last few years data have been obtained for new absolute calibrations for all three operational cameras. Announcements of calibration improvements are published in the IUE Newsletters. RDAF users will find the absolute calibrations used in the software to be current. A summary of present calibrations follows, with further discussion given in the IUE Data Analysis Guide (Grady and Taylor 1989).
Low-Dispersion Calibration:
| LWR and SWP | Holm et al. 1982 |
| LWP | Cassatella, Lloyd, and Gonzalez-Riestra 1988 |
High-Dispersion Calibration:
| Spectra processed before | |
| November 10, 1981 (GSFC) | Cassatella, Ponz, and Selvelli 1981 |
| March 11,1982 (VILSPA) |
| Spectra processed subsequently | Cassatella, Ponz, Selvelli, and Vogel 1990 |
| to the present (all cameras) |
Large Aperture Size for Trailed and Extended Sources:
| LW | SW | ||
| Trail length (arc seconds) | 21.3±1.0 | 21.4±0.4 | Oliversen 1987;Crenshaw and Park 1989 |
| Trail width (arc seconds) | 9.3±0.1 | 8.9±0.3 | Panek 1982b |
| Area (square arc seconds) | 203.±6. | 200.±5. | Panek 1982a |
Exposure Length: LWP, LWR, and SWP:
t
= 0.4096 · INTEGER(t
/0.4096) - R/F time
| R/F time = | LWP | 0.127±0.003 | Schiffer 1980b |
| SWP | 0.129±0.005 | Gonzalez-Riestra et al. 1990 | |
| LWR | TBD |