The human presence on the Moon did not end with Gene Cernan’s final footsteps, nor with Jack Schmitt’s final words before the Apollo 17 lunar module launched from the lunar surface on December 14th, 1972. The remnants of the six Apollo endeavors will, of course, remain on the lunar surface indefinitely as monuments of 20th Century space exploration. But for five years after Apollo 17, a human presence on the Moon was maintained through a collection of experiments at each landing site called the ALSEP program.
Down-Sun picture of the Lunar Mass Spectrometer with the main hub and antenna in the background. (Image from the Apollo Lunar Surface Journal)
Over 5000 ARCSAV tapes were produced during the years of ALSEP data collection, and today most of these are missing
When the Apollo Lunar Surface Experiments Package (ALSEP) program was terminated on September 30th, 1977, it brought an end to 8 years of continuous data collection on a planetary body – a record that would stand (I believe) until Opportunity rolled past 3000 sols in 2012. And, much like Opportunity, ALSEP experiments long outlived their nominal one-year lifetimes. The ALSEP program relayed real-time data on seismicity (natural and astronaut-made), solar wind strength, ion flux, shallow surface heat flow and more to the distributed Manned Space Flight Network on Earth. Analog magnetic tapes (14-track range tapes) from the distributed network were collected at the Johnson Space Center (JSC) for further processing and re-recording. Range tapes made between November 1969 and February 1973 were to be permanently archived at Goddard Space Flight Center. Between 1973 and February 1976, a day’s worth of data from each site were stored onto separate magnetic tapes (7-track digital ARCSAV tapes) so range tapes could be recycled. Data processing was moved offsite (1976-1977) to the University of Texas, where the use of ARCSAV tapes were replaced by 9-track digital tapes (work tapes). And throughout this eight year period, numerous tapes were made for preliminary reports by PIs (PI tapes). Well over 5000 ARCSAV tapes were produced during the years of ALSEP data collection, and today most of these are missing.
In fact, if this tape rack represented the entirety of the ALSEP data collection, we would only have about three tapes (Image by fastlizard4 on Flickr)
The extended-mission life of ALSEP operations created some unanticipated issues for PIs. For example, the six passive seismic experiments recorded data 24-hours a day, enough to fill over one thousand range tapes per year for each site. The ever-growing volume of data tapes were increasingly difficult for PIs to work with, though this was abated somewhat by transferring to higher data-density tapes. The sharp decline in post-Apollo funding – NASA’s budget dropped by a third in the 1970’s – meant some PIs could not devote the hours necessary for data processing and maintenance. Although PIs were instructed to archive tapes with the Washington National Record Center (WNRC), the requirements were vague and poorly enforced and so only an estimated 50% of the PI data were archived. In some cases this was only a subset of processed, “scientifically important” data as selected by PI teams.
Records show something like 3270 ARCSAV tapes made between April 1973 to February 1976 were sent to WNRC. Records also show a massive withdrawal of analog tapes from WNRC, prompted by the tape shortage in 1980, which included ~2800 ARCSAV tapes as Goddard Space Flight Center staff searched high and low for reusable/recyclable tapes. Fortunately, the 7-track digital tapes were not their target (the Apollo 11 landing footage tapes were probably not as fortunate), but instead of returning them to WNRC the ARCSAV tapes were stored in the basement of GSFC. Many of these were later destroyed in a 1990 building flood, and the trail of surviving tapes goes cold after they were removed from the basement of GSFC during cleanup.
Modern computers could do so much more with the ALSEP tapes than was previously possible, if only the data were available. The potential was highlighted in the 1990’s when the University of Texas ’76-’77 tapes were reprocessed and made available on the National Space Science Data Center. But a concerted effort to find the missing tapes wouldn’t get off the ground until 2004, when the presidential mandate for space exploration sparked a resurgence in lunar research in terms of both interest and funds. With practically zero ground-truth characterization of the lunar surface (apart from returned samples and meteorites) and lunar atmosphere, the ALSEP program was a natural target for reevaluation. Suddenly there was a call for these tapes that were nowhere to be found. The NLSI Recovery of Missing Data Focus Group was formally convened in 2007 and is a multi-institutional, (mostly) volunteer-run effort led by some of the original ALSEP PIs.
Apollo 12 dust detector PI tape of days 465-468 (Source: Prof. Brian J. O’Brien PI and SpectrumData)
It is through the efforts of the ALSEP focus group that most of what we know of the tapes has come to light. Every year at the Lunar & Planetary Science Forum (in March) and Lunar Science Forum (in July), the group has a side meeting where they share their successes and frustrations. And there have been successes. In 2010, ~450 ARCSAV tapes made between April and June of 1975 were recovered from WNRC. And at some point, a large quantity of ALSEP data was condensed onto microfiche and microfilm, and also backed up on paper. For LPSC this year, an abstract from the group announced the complete restoration of seven lunar data sets. Another eight data sets are in the final stages and will likely be completed by LPSC, with a promise of more to come. In short, many raw data tapes have been recovered…and also some processed data tapes, and reprocessed tapes of processed data tapes, and prints of raw and processed data…now what?
Hopefully “restoration” should hint at something more involved than slapping an ARCSAV tape in a reader and ripping it onto a hard drive like a CD. Well…OK, that is part of it. But unsurprisingly, such tape readers in working condition are increasingly rare, and at least some of the ARCSAV data recovery was outsourced to data recovery/conversion companies or citizens. Prof. Brian J. O’Brien (Australian government) was an original PI for the Early Apollo Surface Experiments Package (EASEP) and ALSEP Dust Detectors (Apollo 11, 12, 14, and 15) and the Charged Particle Lunar Environment experiment (Apollo 14). He maintained possession of a number of original tapes (including the one pictured above), and is working with SpectrumData to recover quality data.
And quality is the other main issue here. Tape quality degrades over time. Converting tape formats can introduce transcription errors. Processed data might be missing metadata on conversion programs, units, calibrations, random transcription errors, or whatever “corrections” the PI deemed necessary. Even in raw data tapes, anomalies occasionally occur because, after all, they came from the Moon.
It’s all the way past those trees and everything. (Photo by poikiloblastic)
Without relevant metadata (including telemetry to assess transmission quality), the tapes would be worse than useless because any product would rest on a flawed foundation. That remains a major obstacle to data restoration. Significant progress in terms of tapes acquired and metadata resolved has been via cooperation with PI teams and their universities, with one PI even lending an ALSEP experiment notebook to scan for use in calibrating a data set. Prior to archiving with the Planetary Data System, data sets undergo peer review. The ALSEP-recovered-data-related abstracts submitted to LPSC this year are a promising sign of the science return we can expect to see from these important datasets in the years to come.
Almost all of the details above are collected from focus group meetings at the NLSI Lunar Science Forum (2011 & 2012), as well as ALSEP Data Recovery Focus Group progress abstracts submitted to the Lunar and Planetary Science Conference (2011 & 2013). My contribution to the focus group thus far has been to introduce myself at the beginning of said meetings.
ALSEP system and experiment reports are available from the LPI website.
Recovered EASEP and ALSEP data sets are archived in the Planetary Data System Geoscience Node.
Related: Lunar Orbiter Image Recovery Program (LOIRP)