The Nascent Heliophysics Digital Observatory (HDO): a Follow-on to the Heliophysics VxOs

We describe an effort to develop the NASA heliophysics digital observatory (HDO) by consolidating and streamlining several discipline-oriented heliophysics virtual observatories (VxOs) that were established over 15 years ago. The HDO development takes full advantage of the Space Physics Archive Search and Extract (SPASE) metadata model (https://spase-group.org) that is now an information model recommended by the COSPAR Panel on Space Weather (2021). The HDO focuses on developing and implementing higher-level data search capabilities so as not to be duplicative of existing data services. The VxOs, with "x" representing any heliophysics subdiscipline, were generally developed as middleware for searching, locating and accessing discipline-oriented resources that are stored in distributed repositories. Because of discipline-orientation, certain general functionalities had to be duplicated across different VxOs and maintained separately. As technology advances, a few of the original VxOs with obsolete architecture have become difficult to maintain and operate. We have now taken steps to consolidate those VxOs developed at the NASA Goddard Space Flight Center, namely the virtual heliospheric, magnetospheric, and wave observatories, into a single virtual observatory, the HDO. In doing so, we are preserving all the advantages and rationale of the virtual observatory paradigm, but with a more streamlined middleware system. COSPAR Panel on Space Weather, Resolutions on Metadata Standards and Data Access, Space Research Today, Volume 212, December 2021, Page 19. https://doi.org/10.1016/j.srt.2021.11.014