Letters of Intent received in 2019

LoI 2021-2120
100y Time Domain Astrophysics from Digitized Astronomical Imaging Plates

Date: 14 June 2021 to 17 June 2021
Location: Cambridge, MA, United States
Contact: Jonathan Grindlay (jgrindlay@cfa.harvard.edu)
Coordinating division: Division B Facilities, Technologies and Data Science
Other divisions:
Co-Chairs of SOC: Jonathan E. Grindlay (Harvard/CfA)
Elizabeth Griffin (NRC Dominion AstroObs)
Chair of LOC: None (None)



1. Completion of Digitization and Data Releases of the Harvard DASCH
(Digital Access to a Sky Century @Harvard) project:
460,000 image plates, covering full sky 1886-1992

2. Extension to other major image plate collections in
China (Shanghai), Germany, and more

3. Key lessons learned; Key Science results; Key software tools developed

4. Extension to astronomical spectra plates

5. Discussion of required plate handling and cleaning, scanning equipment,
data processing, data storage and distribution, and required personnel



This proposed Symposium is timely since it will draw upon the completion of DASCH
to make the broader case for digitization and data releases from other major image
plate collections to undertake and complete similar full-scale projects. This is crucial
for several reasons:

First, the Harvard plates have a conspicuous gap in plate coverage and thus digital
data from c.1953-1968. This was due to the HCO Director Donald Menzel (who succeeded
Harlow Shapley) stopping the massive plate-taking program for financial reasons. His successor,
Leo Goldberg, fortunately had the good sense to re-start the plate program which was finally
stopped in 1992 when Kodak stopped production of astronomical glass plates.

Second, the imminent start of Time Domain observations with the LSST telescope in 2022 will
usher in the era of enormous numbers of transients (most very faint), including extreme transients that
reach magnitudes V = 12 – 16 readily accessible to plate archival data. Digitization of more large plate
collections will greatly augment the DASCH database by providing increased coverage that will
enable identification of more events and better limits on source outburst duty cycles than DASCH
alone can provide.

Third, Time Domain Astronomy at multi-wavelengths (radio, IR, X- and Gamma-rays) is increasing in
Coverage and Cadence (e.g. proposed full-sky imaging X-ray telescopes, and SKA wide-field radio monitoring). This will also greatly benefit from increased historic optical data from digitized plates to
further extend coverage of rare outbursts. Optical full-sky monitoring is already in place (e.g. ASASSN),
as well as deeper partial-sky monitoring (e.g. ZTF). Both will also benefit from more historic optical data
that the additional plate collections can provide, but only if digitized, calibrated, and made available in
proper Data Releases.

The proposed Symposium date in June, 2021, not only marks the completion of DASCH but is also at a time of year when this event can be hosted by the HCO (with auditorium space available) without the conflicts of the academic year (Sep. – May) and ongoing summer programs (Workshops, late June – August).