Posting gap… and intriguing article on “borrowed data”

Apologies to those of you who were interested in this blog; there has been only one posting since the end of August. Shortly after that I went off-air after an accident, and since then I have been recovering. Although not yet officially back at work, I hope I have now reached the point where I can start making some postings again.

To alleviate potential boredom, a friend gave me some back issue of New Scientist to read. The first one I opened was the issue for 20 January, 2007. On page 14, the first paragraph of an article titled “Loner stakes claim to gravity prize” jumped out at me. It read:

“A lone researcher working with borrowed data may have pipped a $700 million NASA mission to be the first to measure an obscure subtlety of Einstein’s general theory of relativity.”

The thrust of the New Scientist piece is that this “lone researcher” had re-analysed another scientist’s analysis of the orbit of a NASA satellite of Mars, and claimed to have found evidence of the Lense-Thirring effect, a twisting of space-time near a large rotating mass, ahead of NASA’s own expensive mission.

Borrowed data? This had to be worth following up! The relevant article is “Testing frame-dragging with the Mars Global Surveyor spacecraft in the gravitational field of Mars” by Lorenzo Iorio, available from http://arxiv.org/abs/gr-qc/0701042. If you check that reference you may note that 3 versions of the article had been deposited by the cover date of the New Scientist piece, but that he is now up to version 10, deposited on 14 May 2007. Checking the “cited by” citations in SLAC-SPIRES HEP shows that this article has been very controversial, with many comments and replies to comments, apparently contributing to the development of the article (although the authors of these comments don’t get any acknowledgments as far as I could see). Nevertheless, it does look like a nice example of the value of an open approach to science. I don’t know how much the final article is now accepted, although it does seem now to form part of a book chapter (L. Iorio (ed.) The Measurement of Gravitomagnetism: A Challenging Enterprise, Chap. 12.2, NOVA Publishers, Hauppauge (NY), 2007. ISBN: 1-60021-002-3).

What about the borrowed data? The Acknowledgments section has: “I gratefully thank A. Konopliv, NASA Jet Propulsion Laboratory (JPL), for having kindly provided me with the entire MGS data set”. He does not give an explicit data citation. It appears however, that Iorio is not referring to the publicly accessible science results accessible from JPL. In section 2, he writes:

“In [24] six years of MGS Doppler and range tracking data and three years of Mars Odyssey Doppler and range tracking data were analyzed in order to obtain information about several features of the Mars gravity field summarized in the global solution MGS95J. As a by-product, also the orbit of MGS was determined with great accuracy.”

Reference 24 is “Konopliv A S et al 2006 Icarus 182 23”, which appears to be “A global solution for the Mars static and seasonal gravity, Mars orientation, Phobos and Deimos masses, and Mars ephemeris”, by Alex S. Konopliv, Charles F. Yoder, E. Myles Standish, Dah-Ning Yuan and William L. Sjogren., in Icarus Volume 182, Issue 1, May 2006, Pages 23-50. In turn, this paper acknowledges “Dick Simpson and Boris Semenov provided much of the MGS and Odyssey data used in this paper mostly through the PDS archive”, and this time there is a relevant data citation: “Semenov, B.V., Acton Jr., C.H., Elson, L.S., 2004a. MGS MARS SPICE KERNELS V1.0, MGS-M-SPICE-6-V1.0. NASA Planetary Data System”. However this presumably represents the source data from which Konopliv et al did their calculations.

(BTW I have yet to find a formal place where JPL PDS define their requirements for data citations, but there are a couple of examples in http://pds.jpl.nasa.gov/documents/pag/MERDSC.doc, and the citation above sticks to that guideline.)

It looks like the “borrowed data” is in fact provided on a colleague-to-colleague basis. It is clear from some of the replies that there was correspondence between Iorio and Konopliv on some matters of interpretation.

Nevertheless, this seems like a couple of useful examples of science being discovered from the analysis of original and derived datasets established for another purpose, and hence of relevance to data curation. And who knows, maybe the $700 million Gravity Probe mission launched by NASA will turn out not to have been necessary after all?

BTW I tried to follow this story through New Scientist’s online service, to which my University has a subscription. I was asked for my ATHENS credentials, which I provided, but was then thrown out on an IP address check, despite using a VPN. How not to get good use of your magazine!