DASCH DR7 Digital Inventory

These files define a "digital inventory" of all of the files archived as part of DASCH Data Release 7 (DR7). DASCH (Digital Access to a Sky Century @ Harvard) was the project to digitize the Harvard College Observatory’s Astronomical Photographic Glass Plate Collection for scientific applications. This irreplaceable resource provides a means for systematic study of the sky on 100-year time scales.

This inventory does not contain the actual DASCH data. Rather, it contains an exhaustive index of all of the DASCH data — virtually all aspects of DASCH's digital existence throughout the project's entire history, up through the DR7 release date (December, 2024). The complete inventory documents 33,791,530 files totaling 745,627,062,858,355 bytes (around 678 TiB) of data. The inventory itself is about 10 GiB in size (decompressed), spread across 3,946 files.

The actual underlying data are currently archived in a set of Amazon AWS S3 buckets and magnetic tapes held by Harvard College Observatory. Most DASCH users are encouraged to access DASCH data via the project's data access services; this inventory should only be of interest to those interested in large-scale duplication of the DASCH data.

The DASCH archive, which is indexed by this inventory, includes:

Full-plate "mosaic" FITS images of more than 428,000 plates, as well as photographs of the plates and their jackets

Astrometric solution data for about 97% of the plates

Photometric calibration data for about 89% of the plates

Lightcurves for all sources extracted from the plates, matched to two separate reference catalogs:

23,574,404,199 measurements calibrated to the APASS DR8 catalog

27,966,413,880 measurements calibrated to the ATLAS-refcat2 catalog

About 166,000 photographs of observing logbooks documenting the plates, and a selection of historical astronomer notebooks discussing them

Derived products, generated from the above, needed to operate the DASCH data access services

Raw "tile" data from two decades of DASCH scanning, as well as supporting calibration and telemetry files

All of the source code behind the DASCH software systems, from scanning to pipeline processing to data access services to end-user analysis

Logs relating to all modern DASCH pipeline processing, data management, and other operations tasks

All available project documentation

All other data files supporting DASCH operations

See the README.md file within the collection for more information about the structure and contents of this inventory. In summary, it organizes the DASCH data files into a virtual hierarchy of names. Associated with each name is a size (in bytes), MD5 digest, and one or more "data URLs" recording locations where that file is archived as of DR7. Every single file has a data URL indicating a location on Amazon's AWS S3 storage service; many files also have one or more copies on magnetic backup tapes heldby Harvard College Observatory.

The inventory is expressed as a collection of plain-text (UTF-8) files using Markdown syntax. There is approximately one such file for each "folder" or "subtree" of the virtual name hierarchy. Each file contains a human-readable preamble describing the folder contents, an optional Markdown table listing any direct-descendant subfolders, and an optional Markdown table documenting any files contained directly within that folder. The intention is that it should be fairly straightforward for both humans to navigate these files, as well as to write software that processes them. While most files are human-scale in size, the largest (Inventory.pipeline_astrometry.md) is about 280 MiB and contains about 1.5 million records.

As of the DR7 release, only some DASCH archive files are directly accessible by third parties. The Starglass website (https://starglass.cfa.harvard.edu/) makes many photographs and "mosaics" (full-plate FITS images) available, and the web APIs supporting this site and the DASCH data access services (see the DASCH site, https://dasch.cfa.harvard.edu/) provide access to additional resources. To duplicate other portions of the archive, you may need to contact Harvard College Observatory. It is hoped that over time, more and more of the DASCH archive will become available for direct download. It is also hoped that additional copies of the DASCH archive will be created and publicized; the best way to ensure the long-term preservation of this dataset is to duplicate it. A major goal of this inventory is to make such duplication tractable.

To the greatest extent possible, it is believed that all of the files documented as part of this archive can be duplicated free of legal encumbrances. Unless documented otherwise, the copyright owner of all copyrightable elements is the President and Fellows of Harvard College. Please see the DASCH website for the most up-to-date guidance regarding image credits and any legal topics relating to this dataset.

Acknowledgments

The DASCH scanning project was the work of literally hundreds of people over multiple decades. Out of the many people who have devoted their time and energy to the project, the essential contributions of a few deserve special recognition: Prof. Jonathan (Josh) Grindlay; Bob Simcoe; Edward Los; Lindsay Smith Zrull; and Alison Doane.

The DASCH project at Harvard is grateful for partial support from NSF grants AST-0407380, AST-0909073, and AST-1313370; which should be acknowledged in all papers making use of DASCH data.

We acknowledge the one-time gift of the Cornel and Cynthia K. Sarosdy Fund for DASCH, and thank Grzegorz Pojmanski of the ASAS project for providing some of the source code on which the DASCH scientific data access portal was based.

The ongoing AAVSO Photometric All-Sky Survey (APASS) has improved DASCH photometric calibration and is funded by the Robert Martin Ayers Sciences Fund.

This inventory and DASCH Data Release 7 were prepared by Peter K. G. Williams in December, 2024.

本系列文件定义了DASCH（Digital Access to a Sky Century @ Harvard，哈佛天空百年数字获取项目）数据发布7（DR7）所归档全部文件的“数字目录”。DASCH是为科学应用而数字化哈佛大学天文台天文摄影玻璃底片馆藏的项目，这一不可替代的资源为以百年时间尺度开展系统性天空研究提供了可能。

本目录并未包含DASCH原始数据，而是收录了所有DASCH数据的详尽索引——涵盖该项目自启动至DR7发布日期（2024年12月）的整个历史中，DASCH数字化形态的几乎所有方面。完整目录共记录33,791,530个文件，总数据量达745,627,062,858,355字节（约678 TiB），目录本身解压后大小约为10 GiB，分散存储于3,946个文件中。

实际的原始数据目前归档于哈佛大学天文台的亚马逊AWS S3存储桶与磁带库中。我们建议大多数DASCH用户通过项目的数据访问服务获取DASCH数据；本目录仅面向有大规模复制DASCH数据需求的群体。

本目录所索引的DASCH归档数据包括：
1. 超过428,000张底片的全画幅“拼接”FITS（Flexible Image Transport System，柔性图像传输系统）图像，以及底片及其套封的照片；
2. 约97%底片的天体测量解算数据；
3. 约89%底片的光度校准数据；
4. 从底片提取的所有源的光变曲线，并匹配至两套独立的参考星表：
- 23,574,404,199条校准至APASS DR8星表的测量数据；
- 27,966,413,880条校准至ATLAS-refcat2星表的测量数据；
5. 约166,000张记录底片信息的观测日志照片，以及讨论这些底片的部分历史天文学家笔记；
6. 从上述数据衍生而来、用于运行DASCH数据访问服务的衍生产品；
7. 20余年DASCH扫描工作产生的原始“分块”数据，以及配套的校准与遥测文件；
8. DASCH软件系统的全部源代码，涵盖从扫描、流水线处理到数据访问服务再到终端用户分析的全流程；
9. 所有现代DASCH流水线处理、数据管理及其他运维任务相关的日志；
10. 所有可用的项目文档；
11. 所有支持DASCH运维的其他数据文件。

有关本目录的结构与内容的更多信息，请参阅归档内的README.md文件。简言之，本目录将DASCH数据文件组织为虚拟命名层级结构。每个命名均关联有文件大小（字节）、MD5摘要，以及一个或多个“数据URL”，用于记录截至DR7发布时该文件的归档位置。每个文件均配有亚马逊AWS S3存储服务上的位置URL；多数文件还附带哈佛大学天文台磁带备份存储上的一个或多个副本。

本目录以UTF-8编码的纯文本文件集合形式呈现，采用Markdown语法。虚拟命名层级的每个“文件夹”或“子树”对应约一个此类文件。每个文件包含描述文件夹内容的可读序言、可选的Markdown表格（列出直接子文件夹），以及可选的Markdown表格（记录该文件夹内直接包含的文件）。其设计目标是既便于人类浏览，也便于编写软件进行处理。尽管多数文件的大小处于人类可读的量级，最大的文件（Inventory.pipeline_astrometry.md）约为280 MiB，包含约150万条记录。

截至DR7发布时，仅有部分DASCH归档文件可由第三方直接访问。Starglass网站（"https://starglass.cfa.harvard.edu/"）提供了大量底片照片与“拼接”全画幅FITS图像，而支持该网站与DASCH数据访问服务的Web API（详见DASCH官网"https://dasch.cfa.harvard.edu/"）则可访问更多资源。若需复制归档的其他部分，您可能需要联系哈佛大学天文台。我们期望随着时间推移，越来越多的DASCH归档数据可直接下载。同时，我们也希望能创建并公开更多DASCH归档副本；确保该数据集长期留存的最佳方式之一便是进行数据复制。本目录的核心目标之一便是让此类复制工作变得可行。

据现有认知，本归档所记录的所有文件均可无法律限制地复制。除非另有说明，所有可版权元素的版权所有者为哈佛学院院长及研究员。有关图像署名及本数据集相关法律问题的最新指南，请参阅DASCH官网。

致谢
DASCH扫描项目历经数十年，由数百位参与者共同完成。在众多为项目投入时间与精力的人员中，以下几位的核心贡献值得特别表彰：乔纳森（乔希）·格林德雷教授；鲍勃·西姆科；爱德华·洛斯；林赛·史密斯·祖鲁；以及艾莉森·多恩。
哈佛大学的DASCH项目感谢NSF资助项目AST-0407380、AST-0909073与AST-1313370提供的部分资助，所有使用DASCH数据的论文均需提及该资助。
我们感谢康奈尔与辛西娅·K.萨罗斯迪基金为DASCH提供的一次性捐赠，并感谢ASAS项目的格热戈日·波伊曼斯基提供了部分支撑DASCH科学数据访问门户的源代码。
正在进行的AAVSO光度全天空巡天（APASS）优化了DASCH的光度校准工作，该项目由罗伯特·马丁·艾尔斯科学基金资助。
本目录与DASCH数据发布7由彼得·K·G·威廉姆斯于2024年12月编制。