EXCITE (Exoplanet Climate Infrared Telescope)

EXCITE is the acronym for EXoplanet Climate Infrared Telescope a balloon-borne infrared spectrometer with a 0.5-meter aperture, specifically tailored for continuous phase-resolved spectroscopy of hot Jupiter-type exoplanets, observing these planets throughout their entire orbits around their host stars. The telescope's near-infrared coverage from 0.8 to 4 micrometers enables it to detect peak emissions and spectral signatures of hydrogen and carbon-bearing molecules, offering insight into the atmospheric composition and thermal structure of these exoplanets. The instrument was developed by a collaboration between the NASA Goddard Space Flight Center, the Arizona State University, Brown University, Cornell University and the University of Maryland by the US, Universitá La Sapienza and Istituto Nazionale di Astrofisica from Italy, StarSpec Technologies Inc. and the University of Toronto from Canada and Cardiff University, University of Oxford and University College London from the UK.

At left we can see a basic scheme of the instrument (click to enlarge). EXCITE incorporates a stable gondola design, based on that of the SuperBIT telescope, with minor modifications to adapt it for EXCITE's specific needs. The gondola consists of three nested frames to ensure stability across three axes, allowing precision pointing and continuous tracking of targets. The inner frame supports the science instrument, which includes the telescope, spectrometer, and other electronic components, achieving fine-pointing control with feedback from a star camera. Solar panels and lead-acid batteries provide power to the system, and operational limitations on elevation and azimuth prevent direct exposure of the telescope to the ground or balloon.

The telescope itself is a 0.5-meter f/12 design constructed from fused silica, with high reflectivity silver coatings optimized for the infrared range. The primary and secondary mirrors are passively cooled by aluminized mylar linings and external baffles, with additional measures to block stray light. The telescope interfaces with the spectrometer through a transfer box, which contains the optical components. Light enters the system through a central aperture, reflects off a tip/tilt mirror for pointing corrections, and passes through a series of dichroic filters that separate wavelengths into short and long channels, directing them to the cryogenic spectrometer.

The spectrometer is compact, high-throughput, and designed to work at a cryogenic temperature of 100 K to reduce thermal emission, with the focal plane cooled to 50 degrees Kelvin. The detector is a Teledyne H2RG, divided into quadrants to read separate sections of the spectrum. The ACADIA readout electronics control the detector, minimizing read noise and allowing a high frame rate. Band-defining filters in the detector package ensure that stray light does not interfere with the intended spectral measurements.

The cryogenic system includes a dewar and two Thales pulse tube cryocoolers to maintain the required low temperatures for the spectrometer and detector. The coolers dissipate heat through a copper-methanol thermosyphon system, connected to radiators that expel heat to space. This configuration enables a more compact and lighter design, which simplifies operations for the balloon flight. Vibrations from the cryocoolers are minimized to ensure that pointing stability remains unaffected.

Balloon launched on: 8/31/2024 at 13:22 UTC
Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US  
Balloon launched by: Columbia Scientific Balloon Facility (CSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Aerostar - SF 39.57 (39.500.000 cuft)
Flight identification number: 745N
End of flight (L for landing time, W for last contact, otherwise termination time): 9/1/2024 at 00:22 UTC (L)
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 10 h 13 m
Landing site: In the Fort Apache Indian Reservation, Arizona, EE.UU

The EXCITE balloon was launched from the Ft. Sumner NASA balloon base at 13:22 UTC on October 31, as mission 745N. The balloon reached float altitude of around 131,000 feet and flew for a total of 10 hours and 13 minutes. The balloon and payload landed in the Fort Apache Indian Reservation in Arizona.

• EXCITE Website  
• Brown researchers to help build telescope to study exoplanet atmospheres News from Brown University
• Design and testing of a low-resolution NIR spectrograph for the Exoplanet Climate Infrared Telescope Proceedings of the SPIE, Volume 13096, Ground-based and Airborne Instrumentation for Astronomy X; 13096A5 (2024)
• Design and testing of a low-resolution NIR spectrograph for the EXoplanet Climate Infrared Telescope Proceedings Volume 12184, Ground-based and Airborne Instrumentation for Astronomy IX; 1218429 (2022)
• Integration and testing of a cryogenic receiver for the Exoplanet Climate Infrared Telescope (EXCITE) Proceedings of the SPIE, Volume 13096, Ground-based and Airborne Instrumentation for Astronomy X; 130963P (2024)
• Kyle Helson Finds EXCITE-ment in Exoplanet Exploration NASA website
• NASA to Launch 8 Scientific Balloons From New Mexico NASA website
• NASA's EXCITE Mission Prepared for Scientific Balloon Flight NASA website
• Observing exoplanets in the near-infrared from a high altitude balloon platform Journal of Astronomical Instrumentation, 8, 1950011 (2019)
• The design and development status of the cryogenic receiver for the EXoplanet Climate Infrared TELescope (EXCITE) Proceedings Volume 12184, Ground-based and Airborne Instrumentation for Astronomy IX; 121842I (2022)
• The Exoplanet Climate Infrared TElescope (EXCITE) Proceedings of the SPIE, Volume 10702, 107025G (2018)
• The EXoplanet Climate Infrared TElescope (EXCITE) Proceedings Volume 12184, Ground-based and Airborne Instrumentation for Astronomy IX; 121840V (2022)
• The Exoplanet Climate Infrared Telescope (EXCITE): gondola pointing and stabilization qualification Proceedings of the SPIE, Volume 13094, Ground-based and Airborne Telescopes X; 139044Y (2024)