Point of Contact: Jim Buckley (PI) [buckley@wustl.edu]
Status: Proposed – planned to launch in 2024

Brief Description: ADAPT is a demonstration version of the Advanced Particle-astrophysics Telescope (APT), a large satellite experiment for gamma-ray astronomy research. Combined with other detectors, like the LIGO gravitational wave observatory, APT would form a key component for multi-messenger astronomy.

APT was conceived to address two big questions: determining the nature of dark matter and understanding the physics of neutron-star mergers and their role in the origin of the heavy elements. To achieve these goals requires improving gamma-ray sensitivity from the MeV to GeV energies by at least an order of magnitude compared to existing experiments, but without a corresponding increase in mission cost.

See Also: APTlite, APT Note: https://pos.sissa.it/395/655/pdf
https://source.wustl.edu/2021/06/buckley-awarded-4-9-million-to-develop-gamma-ray-astronomy-mission/

Point of Contact: Steven Boggs (PI) [seboggs@ucsd.edu]
Status: Balloon program inactive since Small Explorer (SMEX) satellite study approved

Brief Description: The Compton Spectrometer and Imager (COSI) is a soft gamma-ray survey telescope (0.2–5 MeV) designed to probe the origins of Galactic positrons, uncover the sites of nucleosynthesis in the Galaxy, perform pioneering studies of gamma-ray polarization, and find counterparts to multi-messenger sources. COSI’s compact Compton telescope combines improvement in sensitivity, spectral resolution, angular resolution, and sky coverage to facilitate groundbreaking science.

Note: Now COSI SMEX, PI John Tomsick [jtomsick@berkeley.edu], due to launch 2025

Point of Contact: Julie McEnery
Status: Currently doing beam tests; test flight planned for 2023

Brief Description: ComPair is a short-duration balloon instrument containing prototypes for each subsystem of the proposed All-sky Medium Energy Gamma-ray Observatory (AMEGO), a NASA-led Probe-class mission concept recently submitted to the Astro2020 Decadal Survey. AMEGO is a combined Compton / pair-production telescope with sensitivity from ~ 200keV to above 10GeV, which will provide unprecedented sensitivity in the historical “MeV gap.” AMEGO will study pulsars, magnetars, dark matter, active galactic nuclei (AGN), nuclear lines, and be a useful tool in the era of multimessenger astrophysics.

Point of Contact: Angela Olinto (PI) [aolinto@uchicago.edu]
Status: due to launch Spring 2023

Brief Description: EUSO-SPB2 is a precursor for a next generation space observatory for multi-messenger astrophysics. The EUSO-SPB2 instrument will measure PeV and EeV-scale cosmic rays, optical backgrounds that could mimic tau neutrino interactions in the Earth's limb, and search for optical signatures consistent with the upward-going candidate events reported by the Antarctic Impulse Transient Antenna (ANITA).

Point of Contact: Charles Hailey [chuckh@astro.columbia.edu]
Status: First flight planned for late 2022

Brief Description: GAPS (General AntiParticle Spectrometer) is an Antarctic balloon mission that will search for low-energy (&#lt; 0.25 GeV/n) cosmic-ray antinuclei. GAPS is designed to precisely measure the flux of low-energy cosmic-ray antideuterons, antiprotons, and antihelium. To date, there has not been an unambiguous observation of cosmic-ray antideuterons or antihelium, and observation by GAPS of even a single antideuteron could tell us about the particle nature of dark matter.

Point of Contact: Mark McConnell [Mark.McConnell@unh.edu]
Status: Ongoing

Brief Description: The Gamma-RAy Polarimeter Experiment (GRAPE) is a concept for an astronomical hard X-ray Compton polarimeter operating in the 50 - 500 keV energy band. The instrument has been optimized for wide-field polarization measurements of transient outbursts from energetic astrophysical objects such as gamma-ray bursts and solar flares.

Point of Contact: Scott Wakely [wakely@ulysses.uchicago.edu]
Status: First flight planned for 2022

Brief Description: HELIX is a balloon-borne experiment designed to make measurements of the composition of light cosmic rays in the energy range from below 1 GeV/n to 10 GeV/n, with a specific emphasis on the determination of astrophysically important isotopic abundance ratios.

Point of Contact: Al Kogut (PI) [alan.j.kogut@nasa.gov]
Status: Third flight (1st science) planned for Sept/Oct 2022

Brief Description: PIPER is a balloon-borne telescope that measures the cosmic microwave background polarization on large angular scales, in search of primordial B-modes, created by inflationary gravitational waves. PIPER consists of two co-aligned telescopes, each mapping over half of the sky at four frequency bands between 200 to 600 GHz.

Point of Contact: Abigail Vieregg (PI) [avieregg@kicp.uchicago.edu]
Status: Scheduled to fly December 2024

Brief Description: PUEO is a balloon mission designed to launch from Antarctica that will detect signals from energetic neutrinos, particles that contain valuable clues about the distant astrophysical processes, including the origin of the most energetic cosmic rays in the universe. They can also inform our understanding of active galaxies and neutron star mergers, among other extreme astrophysical environments. Neutrinos travel across the universe undisturbed, carrying information about events billions of light years away. PUEO would be the most sensitive survey of cosmic ultra-high energy neutrinos ever conducted.

Note: PUEO is a successor to the Antarctic Impulsive Transient Antenna (ANITA).

Point of Contact: William Jones [wcjones@princeton.edu]
Status: Ongoing

Brief Description: SPIDER is a balloon-borne mm-wave polarimeter borrowing heavily on the combined heritage of the successful BOOMERANG and Bicep experiments. Its primary objective is to study the genesis of the early Universe, probing fundamental physics at energy scales that are far beyond the reach of terrestrial particle accelerators.

Note: https://astronomy.com/news/2021/01/flight-of-the-spider

Point of Contact: Barth Netterfield [netterfield@astro.utoronto.ca]
Status: Ongoing

Brief Description: SuperBIT is a highly-stabilized, high-resolution visible/near-UV telescope that operates in the stratosphere via NASA's super-pressure balloon (SPB) system. SuperBIT's primary science goal is to provide insight into the distribution of dark matter in galaxy clusters and throughout the large-scale structure of the universe.

Note: https://slate.com/technology/2021/07/superbit-space-balloon-telescope.html

Point of Contact: Brian Rauch [brauch@physics.uwstl.edu]
Status: 2012–2013 (SuperTIGER), 2019–2020 (SuperTIGER-2)

Brief Description: SuperTIGER was developed to measure the abundances of galactic cosmic-ray elements with individual element resolution and the high statistics needed to test models of cosmic-ray origins. SuperTIGER also makes exploratory measurements of the abundances of elements with 40 < Z ≤ 60 and measures the energy spectra of the more abundant elements for Z ≤ 30.

Point of Contact: Henric Krawczynski [krawcz@uwstl.edu]
Status: Flights planned for mid-2022 and late 2023

Brief Description: XL-Calibur is a hard X-ray (15–80 keV) polarimetry mission operating from a stabilized balloon-borne platform in the stratosphere, measuring the X-rays from black holes and neutron stars in our galaxy. It builds on heritage from the X-Calibur mission, which observed the accreting neutron star GX 301-2 from Antarctica, between December 29th 2018 and January 1st 2019.

Point of Contact: Massimiliano Galeazzi (U. Miami, FL) [galeazzi@physics.miami.edu]
Status: Continuing (first launch 2012, latest 2022)

Brief Description: DXL hopes to shed light on the sources of soft X-rays that hurtle towards Earth from elsewhere in our galaxy. DXL is composed of two large area (500 cm² each at 1 keV) thin window proportional counters that were used to produce the original UW all-sky soft X-ray maps. The large area of the proportional counters will provide excellent counting statistics when scanning the sky though the He focusing cone in the limited observing time of a sounding rocket flight. For the scan, the DXL team have chosen a region sufficiently close to the galactic plane to absorb soft X-rays produced outside the solar system and its local environment (within ~100 pc), therefore minimizing the intensity and structure of the cosmic background, as indicated by the Rosat All Sky Survey (RASS).

Point of Contact: Enectali (Tali) Figueroa-Feliciano (Northwestern U., IL) [enectali@northwestern.edu]
Status: Continuing (First launch 2018, next 2022)

Brief Description: Micro-X is a NASA-funded sounding rocket program that will observe Supernova Remnants and search for keV-scale sterile neutrino dark matter. The payload is an X-ray imaging spectrometer, consisting of an X-ray grazing-incidence optic, an optical bench, a cryogenic detector, and associated electronics. The 128 pixel TES-based microcalorimeter array has 4–10 eV FWHM energy resolution at 1 keV. This superior energy resolution allows Micro-X to take unprecedented spectra of various astronomical objects. Micro-X combines the excellent energy resolution of Transition Edge Sensor microcalorimeters with the imaging capabilities of a conical imaging mirror to map extended and point X-ray sources with an unprecedented combination of energy and spatial resolution.

Point of Contact: Randall (Randy) McEntaffer (Penn State U.) [rlm90@psu.edu]

Brief Description: OGRE is a suborbital rocket payload that will fly a high-resolution soft X-ray grating spectrometer. Anticipated to launch in late 2021, the spectrometer will seek to obtain the highest resolution soft X-ray spectrum to date of its target – Capella. To achieve this ambitious goal, the spectrometer will consist three cutting-edge technologies: a mono-crystalline silicon X-ray optic module manufactured by NASA Goddard Space Flight Center, six reflection grating modules developed by Penn State, and four electron-multiplying CCD detectors developed by XCAM Ltd. and The Open University in the United Kingdom.

Point of Contact: Randall (Randy) McEntaffer (Penn State U.) [rlm90@psu.edu]

Brief Description: The Rockets for Extended-Source X-ray Spectroscopy (tREXS) are a series of suborbital rocket payloads that will fly a diffuse soft X-ray grating spectrometer. The first tREXS launch is anticipated for Q3 2022, with a second launch in 2022. The spectrometer consists of passive, mechanical focusers, arrays of reflection gratings, and a focal plane consisting of CIS 113 CMOS detectors. The instrument, which has a field-of-view > 10 sq. deg., will seek to obtain the most highly-resolved spectra of diffuse soft X-ray emission from the Cygnus Loop (2022) and Vela (2022) supernova remnants.