Data Management Division's (DMD) Role in Supporting GSEG-3

M. Kyprianou (kyp[at] and F. Abney (abney[at]

The James Webb Space Telescope (JWST) recently passed a milestone event in its path to launch and eventual arrival at Lagrange 2 (L2), where it will usher in the next phase of humankind's exploration of the cosmos. That event was the successful completion of Ground Segment‑3 (GSEG‑3). This test was the first time that the fully assembled JWST observatory completed an end-to-end processing cycle, starting with the entry of a scientific proposal, and ending with the storage and distribution of scientific data. The JWST Science & Operations Center (S&OC) at STScI, an element of the ground segment, is where the JWST data are processed, stored, and made available for distribution to scientists around the world. This last step in the flow—the data receipt, processing, storage, and distribution—is where STScI’s Data Management Division (DMD) comes into play.

DMD is an engineering and operations division at STScI, whose charter is to provide processing, storage, analysis, and distribution services in support of science data for the multitude of missions whose data are stored in the Mikulski Archive for Space Telescopes (MAST) through an engaged and diverse team. DMD transitioned this diverse team over the last two years to cross-branch and cross-divisional SCRUM teams to improve alignment with its large customer base, while improving execution efficiency. This transition allows for faster build turn around, enhanced testing, and inclusion of features on an earlier cadence than is typically feasible with a non-agile approach.   

DMD's involvement with JWST started many years ago with the definition of functionality for data processing within the S&OC. This functionality resulted in the specification of the JWST Data Management Subsystem (DMS), which is one of the six subsystems that combine to provide the needed functionality for the JWST S&OC. DMS is responsible for data receipt, processing, storage, distribution of engineering and science products, and analysis tools for use by the astronomical community. This functionality is defined and measured by ~700 requirements that encompass its capabilities. The implementation and verification of these requirements drove the development and build schedule.

flowchart from scheduling to archiving
Figure 1: The DMS subsystem as part of the overall operations system for JWST.

Over the last few years, the DMD teams completed multiple builds to address the requirements of DMS. These builds were used for numerous S&OC level tests and rehearsals, including science data generation, simulating commissioning activities, normal day-to-day operations, as well as critical Wave Front Sensing & Control activities, crucial to focusing the 18 multi-segmented mirrors that comprise JWST's primary mirror.

Culminating with the official GSEG‑3 Run for Record, there were 13 preliminary GSEG‑3 events; exercises (subsets of the entire test), rehearsals, and dry runs on various simulator platforms. During the official GSEG‑3, each instrument was powered up, run through a set of commands to generate science data, and then powered down. The data generated were flowed through the Deep Space Network to the S&OC and processed into science products that were retrievable by science instrument teams. The test ran for five days, around the clock. DMD provided operational coverage which monitored the data flow and processing into science products, as well as data browsing with previews and multiple download capabilities.

In the 18 months preceding GSEG‑3, there were numerous DMS builds and patches carried out in a fast-paced engineering environment. In addition, we also had the added twist of dealing with a global pandemic. The last set of five tests were run and supported during the COVID‑19 pandemic. DMD's work was affected as we transitioned to a "work-from-home" mode, but we quickly adapted to our new work restrictions and were able to effectively support the GSEG‑3 tests from locations scattered around the Baltimore metropolitan area. The testing has prepared us for launch, and allowed us to adapt and adjust the S&OC to the intricacies of JWST's behavior, as well as to the integration of the S&OC as a whole. 

As we look forward for JWST, there is one more final end-to-end test prior to launch, GSEG‑4. Of course, DMD is actively engaged, doing our part in coordination with the multitude of teams that will make JWST a success once it reaches its new "home" at L2 and begins science operations.