Example of precovery images showing Jupiter’s moon Valetudo. The moon was discovered in 2017 but later found in this archived shot from 2003. Each of three images in the gif were taken 21 minutes apart.
9 August 2023
Precovery is a term originating in the astronomy community that refers to the finding of evidence of an astronomical object’s existence in archival images and data after the object has been discovered. Precover is also a verb. The term is a blend, or portmanteau, either of pre- + [dis]covery or of pre[-discovery re]covery. The word has been in use by astronomers for over thirty years, but has yet to make it into any of the major general dictionaries, probably because the term rarely appears outside of astronomical papers and such jargon rarely makes it into general dictionaries.
The earliest use of precovery, in the plural form precoveries, that I’m aware of is in a 1991 paper in the Australian Journal of Astronomy:
Another classification of observation we term “precoveries.” These are newly discovered NEAs for which we have identified observations on UKST [U.K. Schmidt Telescope] plates taken in the past. Accurate measurements of these plates thus allow the orbits to be immediately determined, and thus the objects secured.
The use of “we term” hints that this may be the actual coinage of the word, but all we can say for certain is that it indicates the word was quite new in astronomical circles in 1991.
The verb is in place by 1995, when it is used in a paper given at the International Astronomical Union Colloquium of that year:
The asteroids of most interest to us are those which approach the Earth, and whenever such an object is found (by anyone) we perform back-integrations in order to determine whether the object may have been recorded on any UKST plate taken since 1973. In many cases the object is found (“precovered”) and measured, allowing an accurate orbit to be determined soon after its discovery.
That same paper also uses the noun:
Recently a similar object, (5145) Pholus = 1992 AD, was found by the University of Arizona Spacewatch team. The earliest images of Pholus were measured from UKST plates taken in 1977 and 1982. These images were identified following the “precovery” (or pre-discovery recovery) of the object by E.M. and C.S. Shoemaker on films taken with the 0.46 m Palomar Schmidt, and by J.Mueller on plates taken with the 1.2m Palomar Schmidt.
The term continues to appear in the ensuing decades, but in most instances it remains within quotation marks or is otherwise explained, indicating the authors or journal editors did not think it would be familiar to a large portion of their readership. There is this from Astronomy & Astrophysics in 2001:
The Arcetri Near Earth Object Precovery Program (ANEOPP) is a project dedicated to the identification of Near Earth Objects (NEOs) on past archival materials, an activity usually referred to as precovery.
And this from the 2001 book Collisional Processes in the Solar System:
It involves a specific agreement with the MPC [Minor Planet Center] on the share of specific responsibilities, the set-up of new observatories in locations where there are none or only a few, an inquiry on the content and location of image archives that may reveal a "gold mine" for past, undetected observations of newly discovered objects (usually called prediscoveries, or "precoveries"). This last possibility is of great interest, as has been recently demonstrated by the precovery of the NEO [Near-Earth Object]1997 XF11 in films taken at Palomar in 1990 by the teams of E.F. Helin and of E.M. and C.S. Shoemaker: these precoveries have transformed a few-months arc into an 8-years arc, allowing a far better determination of the orbit of this rather intriguing PHO [potentially hazardous object].
There is an example of the word used without marking or comment in a 2010 PhD dissertation:
These observations were used to calculate an orbital ephemeris, and to precover additional data from 10 nights in 2005, as well as 7 subsequent nights in 2007.
But that may show the difference between more informal of the term by astronomers and how the term is presented in journals—unlike dissertations—that have copyeditors who look out for such terms. Here is an example of the term placed within quotation marks in a 2021 article in the Astronomical Journal:
We developed simulations that demonstrated the ability to use archival photometric data in combination with TESS to “precover” the orbital period for these candidates with a precision of several minutes, assuming circular orbits
Occasionally, precovery makes its way out of the confines of astronomy circles and into general publications. The earliest that I have found is in a 9 April 2005 article in the Washington Post about an asteroid that passed close to earth. The article was reprinted in a number of other papers in the following days:
By Dec. 26, the impact probability had risen to one chance in 38. What the plotters needed was a “precovery,” an overlooked observation from before Tholen’s initial June fixes to yield a more precise orbital solution.
In Tucson, astronomers at the Spacewatch Project, at the University of Arizona’s Lunar and Planetary Laboratory, started searching their archive. Spacewatch has been surveying the solar system for 20 years, and precovery is a specialty.
Precovery is a nice example of how a technical term can circulate within a particular discourse community for decades before anyone outside that community notices it.
Sources:
Boattini, A., et al. “The Arcetri NEO Precovery Program.” Astronomy & Astrophysics, 375.1 (15 August 2001), 293–307 at 293. DOI: 10.1051/0004-6361:20010825.
Burkhardt, G., et al. Astronomy and Astrophysics Abstracts: Literature 1991, Part 2. Berlin: Springer, 1992, 631. SpringerLink.
Carusi, A. “NEO, The Spaceguard System and the Spaceguard Foundation.” In Collisional Processes in the Solar System. Mikhail Yakovlevich Marov and Hans Rickman, eds. Astrophysics and Space Science Library 261. Dordrecht: Springer 2001, 341. SpringerLink: Springer eBooks.
Gugliotta, Guy. “Earth Dodges Big One, For Now.” Washington Post, 9 April 2005, A6-1. ProQuest Historical Newspapers.
Kaib, Nathan A. “Numerical Models of Oort Cloud Formation and Delivery.” PhD Dissertation, University of Washington, 2010, 134. ProQuest Dissertations & Theses Global.
McNaught, R. H., et al. “Near-Earth Asteroids on Archival Schmidt Plates.” International Astronomical Union Colloquium, 148, 1995, 170–173 at 170 and 171. CambridgeCore: Proceedings of the International Astronomical Union.
Steel, D. and R. H. McNaught. “The Anglo-American Near-Earth Asteroid Survey.” Australian Journal of Astronomy, 4.2, October 1991, 42–48 at 47.
Yao, Xinyu, et al. “Following Up TESS Single Transits with Archival Photometry and Radial Velocities." The Astronomical Journal, 161.3, 16 February 2021, 1–14 at 1. DOI: 10.3847/1538-3881/abdb30.
Photo credit: Brett J. Gladman/Canadian Astronomy Data Centre, 2003. Taken with the Canada-France-Hawaii Telescope's MegaPrime CCD camera. Wikimedia Commons. Licensed under a Creative Commons Attribution-Share Alike 4.0 International license.