The literature search of Pierce (1975) lists publications containing micrometric and photographic Phoebe observations over the period 1898 to 1969. Bec-Borsenberger & Rocher (1982) extend the list to include photographic observations from 1975 to 1981. In addition, they provide several photographic observations made at La Silla in 1981 which apparently have not been published elsewhere. The only observations published subsequent to 1981 appear to be those made at La Silla in 1982 (Debehogne 1984). The U.S. Naval Observatory (Rohde 1994) and McDonald Observatory (Whipple 1992, 1995) supplied recent unpublished photographic observations, and McDonald Observatory (Whipple 1996) supplied unpublished CCD observations. Requests for the unpublished USNO and McDonald observations must be made to the respective observers. During its encounter with Saturn in 1981, the Voyager 2 spacecraft acquired eight images of Phoebe against a star background. Appendix B provides position measures derived from these images.
Table 2 (click here) summarizes of all of the currently available Earthbased observations grouped into sets. The first column contains the year of the observations; the second and third columns identify the observatory and instrument. A reference or publication is given in column four (see the References section of this paper). Finally, the code number in the last column uniquely identifies the observation set.
| Year | Observatory | Instrument | Reference | Code |
| 1898 | Arequipa | 24 in Bruce | Pickering (1908) | 1 |
| 1899 | Arequipa | 24 in Bruce | Pickering (1908) | 2 |
| 1900 | Arequipa | 24 in Bruce | Pickering (1908) | 3 |
| 1902 | Arequipa | 24 in Bruce | Pickering (1908) | 4 |
| 1904 | Arequipa | 24 in Bruce | Pickering (1905a,1905b) | 5 |
| 1904 | Yerkes | 40 in refactor | Barnard (1905) | 6 |
| 1904 | Lick | Crossley reflector | Perrine (1904) | 7 |
| 1905 | Arequipa | 24 in Bruce | Pickering (1906a) | 8 |
| 1905 | Lick | Crossley reflector | Albrecht & Smith (1909) | 9 |
| 1906 | Lick | Crossley reflector | Perrine (1909) | 10 |
| 1906 | Arequipa | 24 in Bruce | Pickering (1906b) | 11 |
| 1906 | Arequipa | 24 in Bruce | Pickering (1906c) | 12 |
| 1906 | Yerkes | 40 in refactor | Barnard (1906) | 13 |
| 1907 | Greenwich | 30 in reflector | Christie (1909) | 14 |
| 1908 | Lick | Crossley reflector | Perrine (1909) | 15 |
| 1908 | Greenwich | 30 in reflector | Christie (1910) | 16 |
| 1909 | Greenwich | 30 in reflector | Christie (1911) | 17 |
| 1910 | Greenwich | 30 in reflector | Christie (1912) | 18 |
| 1912/13 | Yerkes | 40 in refactor | Barnard (1913) | 19 |
| 1913 | Yerkes | 40 in refactor | Barnard (1914) | 20 |
| 1922 | Yerkes | 24 in reflector | van Biesbroeck (1922) | 21 |
| 1940 | Mt. Wilson | 100 in reflector | Nicholson & Richmond (1944) | 22 |
| 1942 | McDonald | 82 in reflector | van Biesbroeck (1944) | 23 |
| 1952 | Cordoba | Normal astrograph | Bobone (1953) | 24 |
| 1955 | Yerkes | 24 in reflector | van Biesbroeck (1956) | 25 |
| 1955 | McDonald | 82 in reflector | van Biesbroeck (1956) | 26 |
| 1957 | Bloemfontien | ADH telescope | van Biesbroeck (1958) | 27 |
| 1960 | Flagstaff | 40 in reflector | Roemer & Lloyd (1966) | 28 |
| 1968 | Crimean | 40 cm astrograph | Chernykh & Chernykh (1971) | 29 |
| 1969 | Kitt Peak | 213 cm reflector | van Biesbroeck et al. (1976) | 30 |
| 1969 | Catalina | 154 cm reflector | van Biesbroeck et al. (1976) | 31 |
| 1975/76 | McDonald | 2.1 m reflector | Mulholland & Shelus (1980) | 32 |
| 1981 | Lowell, Mesa stn. | 0.33 m reflector | Bowell (1981/82) | 33 |
| 1981 | La Silla | 40 cm GPO | Debehogne (1981a-d/82) | 34 |
| 1982 | Lowell, Mesa stn. | 0.33 m reflector | Bowell (1988) | 35 |
| 1982 | La Silla | 40 cm GPO | Debehogne (1984) | 36 |
| 1992 | USNO | 24 in reflector | Rohde (1994) | 37 |
| 1992 | McDonald | 2.1 m reflector | Whipple (1992) | 38 |
| 1993 | USNO | 24 in reflector | Rohde (1994) | 39 |
| 1994 | McDonald | 2.1 m reflector | Whipple (1995) | 40 |
| 1995/96 | McDonald | 2.1 m reflector | Whipple (1996) | 41 |
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The observations in Set 29 made at the Crimean Astrophysical Observatory are reported together with observations of Hyperion and Iapetus. However, the differential positions of Phoebe relative to those bodies exhibit significant errors in right ascension. For this reason, we preferred the absolute rather than differential positions.
The McDonald observations by Mulholland and Shelus, the Lowell observations by Bowell, and the La Silla observations by Debehogne all include a number of simultaneous observations of other satellites. For these sets we constructed and used satellite-relative rather than the absolute positions.
Rohde's USNO set 37 has a significant bias in right ascension, and his set 39 has a significant bias in declination. Until the sources of these biases are understood, the observations are not usable.
The Voyager observations are the pixel and line locations of the images of Phoebe and background reference stars in the Voyager camera frame. They provide measures of Phoebe's position with accuracies in the 70 to 260 km range. The FK4/B1950 positions of the stars are from a special star catalogue (Klemola et al. 1979) made for the Voyager project and reduced to the Perth 70 catalogue. To facilitate processing of the observations, we rotated the star positions to the FK5/J2000 system following the IAU Commission 20 conversion procedure (Standish et al. 1992).