A New Instrument to Rapidly Characterize Near-Earth Asteroids
Credit: Pixabay/CC0 Public Domain
As new generations of astronomical survey facilities come online, scientists expect a sharp increase in the discovery of near-Earth asteroids, including objects that may pose potential collision risks to Earth. Rapidly characterizing these objects after discovery is critical, and a new instrument currently being built for the NASA Infrared Telescope Facility, or IRTF, on Maunakea, will do exactly that.
Called Spectre, the instrument will rapidly gather spectroscopic observations to determine the composition, size, and mass of asteroids on short timescales. Many newly discovered asteroids are faint, fast moving, and initially difficult to pinpoint, making fast and efficient observations essential for understanding their physical properties and potential risks.
“Spectre is designed to respond quickly to new asteroid discoveries and capture a broad range of wavelengths at the same time,” said Warren Skidmore, IRTF Deputy Director. “That ability allows us to determine what these objects are made of while the opportunity to observe them is still available.”
Spectre achieves this capability through a combination of wide wavelength coverage and its design as an integral field spectrograph. By observing optical through thermal infrared light, from 0.4 to 4.2 microns, the instrument will provide detailed spectral fingerprints that reveal asteroid surface materials, space weathering effects, and signs of hydration. The integral field unit simplifies observations, supports accurate flux calibration, and enables more precise spectra, helping scientists better understand the asteroid-meteorite connection and how these objects evolve over time.
At the heart of Spectre is a compact vacuum-sealed structure that houses three spectrographs, one optical and two infrared, kept at cryogenic temperatures of approximately 180 to 200 degrees Celsius below zero. Preparing this outer vacuum jacket is a critical step in the instrument’s performance. Images from the fabrication process show the interior of the jacket being carefully polished, an innovative technique routinely used by IRTF to reduce the amount of infrared heat the jacket emits into the instrument. Limiting this unwanted infrared flux is crucial for maintaining sensitivity when observing faint celestial targets.
“Everything inside the vacuum jacket is cooled to extremely low temperatures, so even small amounts of infrared heat can impact performance,” Skidmore said. “By polishing the interior surfaces, we significantly reduce the infrared flux entering the instrument, which improves the quality of the data we can collect.”
The instrument’s distinctive purple vacuum jacket has also become a recognizable feature during its development. The color choice, now affectionately referred to as ‘plum crazy,’ came about during a last-minute decision when engineers were unable to settle on a single color, resulting in the bold shade, made iconic through Mopar muscle cars in the 1970s, that quickly became part of Spectre’s identity.
The name Spectre carries its own story as well. As with many instruments at IRTF, the computers that operate Spectre are given themed names. One of those computers will be called Oddjob, a reference to actor Harold Sakata, who portrayed the character in the James Bond film Goldfinger and was also an Olympic weightlifter from Kona. With that connection in mind, and a shared appreciation for Bond films among IRTF staff, the name Spectre was chosen for the instrument as a fitting and playful nod.
Major components of Spectre have already arrived in Hilo, including the completed vacuum jacket. Integration and testing will take place at the Institute for Astronomy facilities before the instrument is installed at IRTF. First light for Spectre is currently anticipated in 2028.
Once operational, Spectre will play a key role in near-Earth object science and planetary defense efforts, while also enabling rapid characterization of supernovae and other transient events discovered by all-sky surveys, deepening our understanding of both small bodies in our solar system and explosive phenomena beyond it.
