Space Studies Board weighs in: NASA should build a space-based infrared NEO survey telescope



…that is, NEOCam – the Near-Earth Object (NEO) Camera, a dedicated space-based infrared NEO survey telescope. I know of no other mission concept of this sort that is in the works.

NASA selected NEOCam for phase-A (concept) study through a Discovery program competition in 2015. In 2017, NASA approved “extended-phase-A” funding for the project. NASA’s planetary defense program (full disclosure: I am a consultant to this program, and no one asked me to write this blog) wants to advance NEOCAM to phase B – design. Higher-ups at NASA appear unwilling, as yet, to advocate for the extra funding needed in the planetary defense budget to develop NEOCAM. (See below.)

As I’ve reported here before, the planetary defense community has been advocating for a space-based NEO survey telescope that will observe in the infrared for some time (see, for example, the NASA Small Bodies Assessment Group’s findings over the past few years). NASA is funding an “extended-phase-A” study of the NEOCam mission.

Why IR? As NEOCam principal investigator Amy Mainzer explains, asteroids typically reflect less than 10 percent of the sunlight that hits them in visible wavelengths. This visible light reflection is what ground-based observers can detect. The rest of the sunlight that hits an asteroid is emitted in infrared wavelengths – hence, the desirability of an IR NEO survey telescope. (Also, a space-based telescope can observe 24/7, while ground-based telescopes can only observe at night when the sky is clear.)

In 2018, NASA chief scientist Jim Green asked the Space Studies Board (SSB) of the National Academies of Sciences, Engineering, and Medicine to investigate and make recommendations about a space-based infrared NEO telescope’s capabilities. The SSB appointed an ad hoc Committee on Near Earth Object Observations in the Infrared and Visible Wavelengths, to explore the relative advantages and disadvantages of infrared (IR) and visible observations of near Earth objects (NEOs), review and describe the techniques that could be used to obtain NEO sizes from infrared observations and delineate any associated errors in determining NEO sizes, and “evaluate the strengths and weaknesses of these techniques and recommend the most valid techniques that give reproducible results with quantifiable errors.”

Over the course of three meetings, the committee was briefed by more than a dozen experts on NEO observations.The committee concluded that a space-based infrared telescope would be “more effective at detecting NEOs than visible wavelength in-space telescopes,” would “provide diameter information that visible wavelength telescopes cannot provide” (as the committee noted, “In addition to detecting NEOs and determining their orbits, it is necessary to estimate their mass to quantify their destructive potential. A NEO’s diameter is the most readily available indicator of its mass”), and would “not cost significantly more than in-space visible wavelength telescopes.”

The committee recommended that if congressionally mandated NEO detection requirements “are to be accomplished in a timely fashion (i.e., approximately 10 years), NASA should fund a dedicated space-based infrared survey telescope. Early detection is important to enable deflection of a dangerous asteroid.”

The committee also recommended that “if NASA develops a space-based infrared near Earth object (NEO) survey telescope, it should also continue to fund both short- and long-term ground-based observations to refine the orbits and physical properties of NEOs to assess the risk they might pose to Earth, and to achieve the George E. Brown, Jr. Near-Earth Object Survey Act goals.”

In congressional testimony on June 11, NASA associate administrator for space science Thomas Zurbuchen said, “NASA’s Planetary Defense Program will continue to fund the NEO Observations project and development of a space-based infrared instrument for detecting NEOs with this year’s budget request. Meanwhile, the Double Asteroid Redirection Test (DART) to demonstrate the kinetic impact technique for asteroid deflection will continue to make progress towards its planned 2021 launch.”

For me, the key words here are “with this year’s budget request.” NASA’s fiscal year 2020 budget request for planetary defense is not sufficient to complete the DART mission and advance NEOCam to development.

On April 29, as reported by Space Policy Online, NASA administrator Jim Bridenstine told attendees at the 2019 Planetary Defense Conference “that he was asked about NEOCam during a recent Senate Commerce Committee hearing,” and that “he would talk to…Zurbuchen, and the director of SMD’s planetary science division, Lori Glaze, about how to fund it. ‘But know this, we are committed to doing that,’ Bridenstine asserted.”

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