An Exercise in Satellite Mission Design

by | Jan 3, 2025 | Daily Paper Summaries, Instrumentation, satellites | 0 comments

Title: MAUVE: An Ultraviolet Astrophysics Probe Mission Concept

Authors: Mayura Balakrishnan, Rory Bowens, Fernando Cruz Aguirre, Kaeli Hughes, Rahul Jayaraman, Emily Kuhn, Emma Louden, Dana R. Louie, Keith McBride, Casey McGrath, Jacob Payne, Tyler Presser, Joshua S. Reding, Emily Rickman, Rachel Scrandis, Teresa Symons, Lindsey Wiser, Keith Jahoda, Tiffany Kataria, Alfred Nash, and Team X

First Author’s Institution: Department of Astronomy, The University of Michigan, Ann Arbor, MI, USA

Status:  Published in Publications of the Astronomical Society of the Pacific, Volume 136, Number 10 [open access]

How do new space-telescopes go from idea to reality? The NASA Mission Design Schools aim to address this by teaching doctoral students, new PhDs, postdocs, and junior faculty more about the process of designing space-based missions. Today’s bite explores a mission developed at the inaugural NASA Astrophysics Mission Design School (AMDS), hosted at the Jet Propulsion Laboratory in 2023, the Mission to Analyze the UltraViolet universE (MAUVE).

MAUVE was designed to fit constraints from the 2023 Announcement of Opportunity for the Astrophysics Probe Explorer (APEX) mission as part of the Astrophysics Explorers Program, which seeks to support small to medium missions (like XRISM, IXPE, and GUSTO) that fill the gaps between larger NASA missions (e.g. JWST, Hubble). While MAUVE was developed to fit the constraints from this mission call, it was not actually submitted and is not being further developed. However, sharing the outline of all the considerations that go into a space-based mission design provides a powerful reference for those interested in proposing a mission in the future! Two proposals did end up being selected for the APEX call–an Advanced X-ray Imaging Satellite (AXIS) and a Probe far-Infrared Mission for Astrophysics (PRIMA)–if you want to follow their development!

Today’s paper outlines the science capabilities and instrument design, spacecraft orbit and control, and cost of MAUVE–a space-based hybrid imaging spectrograph spanning extreme to near UV wavelengths that can be used to study atmospheres of exoplanets, kilonovae, supernovae, and extragalactic emission. In today’s bite we only cover the science capabilities and instrument design, but a future bite will explore MAUVE’s spacecraft orbit and control!

MAUVE’s Motivation

UV wavelengths are only observable from space (or more technically, the upper Earth’s atmosphere) since the Earth’s atmosphere absorbs and scatters most UV light, which is good for humans but sometimes not great for astronomers. Only four NASA-commissioned UV detectors currently remain in space: The Space Telescope Imaging Spectrograph (STIS; on Hubble), The Wide Field Camera 3 (WFC3; on Hubble), The Cosmic Origins Spectrograph (COS; on Hubble), and The Ultraviolet and Optical Telescope (UVOT; on Swift). Developing a new UV focused space mission is especially important because both Hubble and Swift are pretty old space-based telescopes (launched 35 and 20 years ago respectively) even though they were only expected to function for about 10 years. Additionally, none of the remaining detectors can study the extreme UV (EUV, 50-121 nm) or far UV (FUV, 122-200 nm) at the precision, spectral resolution, and duration that the science cases of MAUVE require (see Figure 1).

There are 8 UV space missions depicted on the plot aside from MAUVE. 5 are retired (the Far Ultraviolet Spectroscopic Explorer or FUSE, the Berkeley Extreme and Far-UV Spectrometer on the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrograph, the International Ultraviolet Explorer, the Galaxy Evolution Explorer, and the Extreme Ultraviolet Explorer), 2 are ongoing (Swift's Ultraviolet-Optical Telescope and Space Telescope Imaging Spectrograph and Cosmic Origins Spectrograph on the Hubble Space Telescope), and 1 mission was recently selected (the Ultraviolet Explorer). The proposed capabilities of MAUVE span a larger wavelength range than any prior, ongoing or proposed missions, at a lower resolution of about R of 1,000.)
Figure 1 (Figure 1 in today’s paper): A comparison between the proposed wavelength range and spectral resolution of MAUVE and other retired and ongoing UV focused space-based missions.

MAUVE Science Case

MAUVE has 5 primary science objectives spanning 3 Decadal themes, which are planned to occupy 30% of the observation time (see Figure 2). The remainder of MAUVE’s observation time (70%) is for the general observer program, where scientists can submit proposals to investigate their specific science cases. Today’s paper spends a lot of time referencing the Decadal themes, but what is the Decadal and why is it so important?

The first science objective is “Is Sub-Neptune Atmospheric Escape Due to Photoevaporation or Core-Powered Mass Loss?” and spans extreme UV wavelengths (50-121 nm). The second science objective is “Is the Atmospheric Composition of Hot Gas Giant Exoplanets Influenced by Equilibrium or Disequilibrium Condensation?” and spans the bottom fourth of the far UV (122- 200 nm) and near UV wavelengths (200-300 nm). Both the first and second objective fit into the Astro2020 theme of “Are we Alone / Worlds and Suns in Context.” The third science objective is “Are Blue Kilonovae Drive by Radioactive Cooling or Rapid Shock Cooling?” and spans the last third of the far UV and all of the near UV. The fourth science objective is “Do Type 1a Supernovae Arise from a White Dwarf Accreting Material from a Stellar Companion, or from Merging White Dwarfs?” and spans from the bottom third of the extreme UV and all of the far and near UV. Both the third and fourth science objectives fit into the Astro2020 theme of “How does the Universe Work? / New Messengers and New Physics.” The final science objective is “Does Diffuse Extragalactic Emission Result from Faint Galaxy Cluster Members and Rouge Stars, or Shocks from Cluster Mergers?” and spans all of the extreme and far UV falling into the final Astro2020 theme of “How Did we Get Here? / Cosmic Ecosystem.”
Figure 2 (Figure 2 in the paper): The 5 primary science objectives of MAUVE sorted into their different Astro2020 Decadal Themes and sub-questions (the left hand y-axis) and what range of UV wavelengths the science case spans (the x-axis).

Since astronomy receives limited funding, we have to streamline our science efforts to address the most pressing science questions first. The decadal survey guides what science questions should be prioritized in the following decade, with the most recent decadal survey being Astro2020. If you read white papers for mission concepts, you’ll often find that they highlight how their work relates to the most recent decadal survey, which is basically to say, “You’ll be able to work towards answering the field’s most pressing science questions if you fund our mission!” This isn’t unique to mission concepts either. If you’ve ever written an observing proposal, fellowship proposal, or other proposal for funding, you may have noticed that your advisor will recommend or require you to explicitly state how your research question(s) are connected to the themes and science questions highlighted by the decadal survey, for similar reasons.

The five science themes addressed by MAUVE are:

  • To better understand the gap in the distribution of sub-Neptune radii estimated with Kepler through observations of exoplanet’s atmospheric transmission spectrum and the ionization rate based on the stellar host’s EUV flux which will help determine if planets below the gap lose their atmosphere via photoevaporation or core-powered mass-loss.
  • To improve our understanding of aerosols (clouds and hazes in exoplanet atmospheres) through observations of hot gas giants.
  • To characterize if the cooling mechanism of binary neutron star mergers is coming from radioactive decay (from neutrino “winds” interacting with the mass ejected from the merger) or shock cooling (cooling of matter ejected by a post-merger gamma-ray burst).
  • To determine if type 1a supernovae occur due to a merger of two white dwarfs or from a white dwarf accreting material from a stellar companion.
  • To find out if the excess emission observed from the cosmic UV background (CUVB) comes from faint galaxy cluster members or from merging galaxy clusters.

Instrumentation

The primary instrument on MAUVE is The Hybrid Imager/SpecTrograph for uLtraviolet into Extreme wavelengths (THISTLE) which allows for imaging and spectroscopy between 50 and 300 nm. The optical layout for THISTLE can be seen in Figure 3. Light from the telescope first travels into a wheel including slits of various sizes for slit-spectroscopy (if not in imaging mode). The light is then separated into the EUV or FUV/NUV channels using a dichroic. Both channels include a grating wheel after the dichroic which will include gratings with designs tuned to the primary science cases of MAUVE. Finally, the FUV/NUV channel includes a second, cross-dispersing grating, allowing for higher-resolution echelle spectroscopy. 

The light path from the telescope to the instrument is shown. Light first passes through a collimator and a slit wheel (when spectroscopy is enabled) before meeting a dichroic. The dichroic splits the light into an EUV and FUV/NUV path. The EUV path only contains a grating wheel before reaching the sensor, but the FUV/NUV path contains an optional cross-disperser after the grating wheel that will allow for echelle spectroscopy (higher resolution spectroscopy) for both FUV and NUV.
Figure 3 (Figure 9 in the paper): The proposed optical path of THISTLE on MAUVE.

Conclusion

Even though MAUVE will not be developed further as a space mission, papers like this are great examples of all of the different aspects scientists need to think of when proposing for a mission concept. Developing new instrumentation and missions are integral to the advancement of astronomy, allowing for new observations that help us better understand the fundamentals of our universe. In today’s bite we only covered some of the basics: linking the science questions you want to answer with the Decadal survey and the instrumentation design. But there are many more aspects including coming up with a list of preliminary science targets, plans for how to downlink data, analyze data, and archive data products, planning the orbital position of the satellite, how to maneuver the telescope for observations, and identifying the biggest risks with the project and outlining how to mitigate them, some of which we will cover in the second part of this article coming soon!

Astrobite edited by Alexandra Masegian.

Featured image credit: Adapted from Figure 12 in todays paper.

Author

  • Erica Sawczynec

    I am a fourth year graduate student at the University of Texas at Austin working on NIR spectroscopy instrumentation. When I’m not in the lab I manage the archive for IGRINS (RRISA) and use the data products to study molecular hydrogen emission in circumstellar disks. Outside of work you can find me reading sci-fi and fantasy novels, baking bread, hanging out with my cat, or over on Twitter @EricaSawczynec.

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