Meet Marc Rafelski - Cosmic Origins Spectrograph (COS) Branch Manager at STScI

We are honoring Marc Rafelski in celebration of the 34 years lauch anniversary of Hubble Space Telescope (HST). Currently, Hubble operates with four active instruments: ACS, COS, STIS, and WFC3.

Marc serves as the Branch Manager for the Cosmic Origins Spectrograph (COS) instrument on Hubble, which stands as one of the two ultraviolet (UV) spectrographs on board and holds the title of the most sensitive UV spectrograph in space. He has spearheaded various endeavors aimed at calibrating and prolonging the lifespan of COS.

Over the past four years as the COS team lead, Marc and his team ensure the instrument's functionality, troubleshoot anomalies, and offer assistance to the astronomical community. Guided by Marc's leadership, the COS team has expanded the instrument's longevity through the development of innovative techniques and the introduction of new data products like the Hubble Advanced Spectral Products (HASP).

We spoke Marc Rafelski about his journey at STScI and his contributions to the Hubble Mission

• Can you tell us about the journey at STScI that led to your current role?

?I joined STScI as a support scientist for the instruments division in 2016 as a member of the Cosmic Origins Spectrograph (COS) team. This UV spectrograph loses sensitivity over time as we use different regions of the detector, and we overcome this limitation by placing the light from astronomical sources onto different locations of the detector over time (lifetime positions; LP). While on the team, I led the calibration of the fourth lifetime position (LP4) and produced calibration reference files for it. I also led STScI's contribution to the flight software update managed by NASA Goddard, enabling the instrument to support additional LPs. In addition, I participated in the COS2025 initiative to extend the life of the instrument to 2025. In 2018 I had the opportunity to learn about data archives and how we share data with our users by moving to the archive sciences branch. With them I investigated the best way to make spectroscopic observations available to our community. In 2019 I wanted to use my skills to address the bigger picture through a leadership role, so I became the Wide Field Camera 3 (WFC3) branch deputy, where I learned how to manage a branch while helping improve the calibrations. Finally, in 2020 I became the team lead (branch manager) of the COS team leading numerous new initiatives to provide the astronomical community the best UV spectroscopy and data products possible while developing a fantastic team. During these eight years I also conducted scientific research on the topic of galaxy formation and evolution and how galaxies exchange gas with their surroundings, publishing almost a hundred papers and supporting five postdocs and two interns.?

• ?How have you been supporting the Hubble Telescope?

?I have been the team lead (manager) of the COS team for the last four years. COS is one of the four instruments on the Hubble Space Telescope (HST). My team monitors and calibrates the instrument, addresses anomalies that come up, and provides support to the astronomical community in using the instrument while keeping it safe. I also oversee efforts to extend the lifetime of the instrument, improve our calibrations, and enhance our data products. COS is one of two ultraviolet (UV) spectrographs on HST, and having launched in 2009, is the most sensitive UV spectrograph in space. Under my leadership, the COS team expanded the lifetime of the instrument by developing new ways to utilize additional area at the top of the detector to enable additional LPs and by placing the light from astronomical targets on different regions of the detector, depending on the mode. By doing so we have extended the life of COS allowing sensitive high-resolution UV spectroscopy into the 2030's and beyond. In addition, with a view to improve the data products available for UV spectroscopic data, we recently released the Hubble Advanced Spectral Products (HASP) which provides automatically updated combined spectra of astronomical sources for both UV spectrographs COS and STIS (Space Telescope Imaging Spectrograph).?

• ?What is the most memorable thing about your work with Hubble’s instrumentation?

?The most memorable part of my work with Hubble is the extraordinary people I work with; I have enjoyed working with these creative scientists and engineers to maintain and enhance UV spectroscopy for the astronomical community. In particular, I will always remember working with my team to figure out how to extend the life of the COS instrument such that it will be able to function for the full lifetime of the telescope. I enjoyed thinking outside of the box, coming up with new ideas, and guiding and empowering my team to solve this challenging problem in new way. Their curiosity, creativity, and dedication will inspire me for years to come.

• ?What excites you most about the future of your instrument and the Hubble Telescope?

?We are continually improving the calibrations of the instrument and will soon release an update that significantly improves the wavelength accuracy of COS UV spectra. Specifically, by incorporating improved geometric and walk corrections we can ensure that the photons fall where we expect on the detector, improving the overall calibrations of the instruments. Moreover, the work for the HASP program provided the foundation for an improved Hubble Spectroscopic Legacy Archive (HSLA) which we are working on now. In the future, this will provide automatically updated co-added spectra across programs for individual targets in the archive, organized by type of target for both COS and STIS. This enables scientists to download science-ready spectra in an easy-to-find way and conduct a large range of investigations without having to combine data obtained over multiple years. Lastly, I look forward to continue producing additional lifetime positions with the new area at the top of the detector and coming up with new solutions as needed to ensure that COS works for the remaining lifetime of the Hubble Space Telescope. Our work with Hubble will provide a lasting UV legacy for the next couple of decades until the next big flagship mission with UV spectroscopy, the Habitable Worlds Observatory.?