The NEO Surveyor science data processing pipeline builds our team’s experience with discovering asteroids using a space-based infrared telescope, WISE. Our team developed software that discovered new asteroids and comets in near real-time; the asteroid-hunting portion of the WISE project is known as NEOWISE. 

The NEOWISE software developed by our team allowed us to detect more than 158,000 asteroids and comets (including about 34,000 new discoveries) with heat-sensitive infrared images. These included 577 NEOs (135 of which were new discoveries credited to NEOWISE).

We will adapt the existing NEOWISE science data processing to work with NEO Surveyor’s images, allowing us to distinguish moving asteroids and comets from background stars and galaxies.  NEO Surveyor’s survey cadence is optimized to allow the mission to not only discover new asteroids, but to observe them enough times to ensure that they can be found again.

When a new asteroid or comet is first detected, astronomers don’t know what kind of orbit it has, or how far away it is. Astronomers can report its position in the sky to the Minor Planet Center (MPC), which is sanctioned by the International Astronomical Union. There, astronomers use advanced computer programs to determine the object’s orbit.

The infrared sky has fewer stars. The red dot at the center of this image is the first near-Earth asteroid discovered by NEOWISE. This particular asteroid, called 2010 AB78, is roughly one kilometer (0.6 miles) in diameter, and is currently about 158 million kilometers (98 million miles) away from Earth. The image shows three infrared wavelengths, with red representing the longest wavelength of 12 microns, and green and blue showing 4.6- and 3.4-micron light, respectively. The asteroid appears redder than the rest of the background stars because it is cooler and emits most of its light at longer infrared wavelengths. In visible light, this space rock is very faint and difficult to see.  At visible wavelengths, the sky is blazing with stars, but at the thermal infrared wavelengths NEO Surveyor will use, the stars are often much dimmer than the asteroids, making the asteroids easier to find.  Image credit: NASA/JPL-Caltech/UCLA.

Sometimes, there are too few observations to determine the orbit accurately. When this happens, the worldwide community of amateur and professional astronomers can step up to the plate. Telescopes — from large, million dollar scientific marvels to smaller, backyard setups — can be trained on the sky to acquire more observations of the object. Astronomers then send these observations to the Minor Planet Center, allowing knowledge of the orbit to be improved. In this way, the advanced computer programs used for calculating orbits get more and more accurate over time (~decades).

NEO Surveyor’s Investigation Team, using survey data for discovered objects and orbits determined by the MPC, will calculate diameters, albedos, and impact frequencies for the objects. The impact probability, calculated from the orbit, is used to determine whether an object may be a threat to Earth.  The impact frequency is used to determine *when* the object may impact Earth.

Just as our team did with NEOWISE, the NEO Surveyor science data processing system will allow us to report observations of all potential asteroid discoveries to the Minor Planet Center soon after the images are collected. NEO Surveyor will observe each asteroid enough times over a long enough span of time to ensure that the objects can be recovered by other observers at the next possible observing opportunity from the ground. Once the observations are submitted to the Minor Planet Center, impact probabilities for each object will be automatically computed. In the event that a potential impactor is discovered, officials at NASA Headquarters will be immediately notified according to standard procedures already in place

Comet NEOWISE captured on July 6, 2020 above the northeast horizon just before sunrise in Tucson. Discovered on March 27, 2020 by the NEOWISE space telescope, Comet NEOWISE (or by its formal designation, C/2020 F3) brightened to the point of being visible in the night sky to the naked eye. It was the brightest comet to approach Earth since Comet Hale-Bopp back in 1997. Its closest approach to Earth occurred on July 22. It is a long-period comet and will not visit Earth again for another 6,700 years. Credit: Vishnu Reddy.

The NEO Surveyor Mission will be observing asteroids in the infrared – a range of wavelengths that cannot be seen by the human eye. A telescope operating at these wavelengths will be sensitive to warm objects, like asteroids whose surfaces have been warmed by the sun.

How to Tell the Size of an Asteroid. This chart illustrates how infrared is used to more accurately determine an asteroid’s size. As the top of the chart shows, three asteroids of different sizes can look similar when viewed in visible-light. This is because visible-light from the sun reflects off the surface of the rocks. The more reflective, or shiny, the object is (a feature called albedo), the more light it will reflect. Darker objects reflect little sunlight, so to a telescope from millions of miles away, a large dark asteroid can appear the same as a small, light one. In other words, the brightness of an asteroid viewed in visible light is the result of both its albedo and size. The bottom half of the chart illustrates what an infrared telescope would see when viewing the same three asteroids. Because infrared detectors sense the heat of an object, which is more directly related to its size, the larger rock appears brighter. In this case, the brightness of the object is not strongly affected by its albedo, the measure of how bright or dark its surface is. When visible and infrared measurements are combined, the albedos of asteroids can be more accurately calculated. (Image credit: NASA/JPL-Caltech.)

If you look at the sky on a dark night, your eyes will see tens of thousands of stars. Although beautiful, these bright stars can act as camouflage, hiding the dimmer asteroids and comets we want to spot. However, look at the same night sky with a heat-sensing infrared camera, and many of the bright stars are filtered out, leaving the asteroids and comets clearly visible.

Ground-based surveys that scan the sky for hazardous asteroids in visible wavelengths are most sensitive to more highly reflective asteroids. Like someone wearing a white T-shirt at night, light-colored asteroids are easier for visible light telescopes to spot. Darker asteroids tend to be fainter at visible wavelengths, making them difficult to detect with this type of telescope.

NEO Surveyor’s infrared cameras are equally sensitive to dark and bright asteroids. Like a black T-shirt on a hot summer’s day, darker asteroids absorb more heat than more reflective asteroids. Hotter asteroids shine brighter in infrared wavelengths, making them equally easy to spot with NEO Surveyor.

Not only will NEO Surveyor be sensitive to dark asteroids, but infrared observations can also be used to make accurate measurements of an asteroid’s size.  Unlike visible light telescopes, which have a tough time distinguishing between asteroids that are small but highly reflective and those that are large and dark, an infrared telescope can usually measure an object’s effective diameter to within about 10%. 

The infrared cameras on NEO Surveyor will need to be kept cold in order to function properly. Previous missions, such as WISE, relied on expensive cryogens for refrigeration. Cryogens limit the life of the mission — once the cryogens are used up, the camera’s usefulness decreases dramatically. NEO Surveyor sidesteps this issue by operating at the L1 Lagrange point and employing a sun shield, so that it can remain cool and cryogen-free throughout its five-year mission.

The baseline mission requirements are:

NEO Surveyor is the flight mission which originated from the NEOCam mission proposed by Dr. Amy Mainzer to the Discovery Program in 2014.  NEOCam was approved for Extended Phase A study to further refine the technical design and perform risk reduction activities.  The Extended Phase A completed System Readiness Review / Mission Design Review in February 2018, and a pre-KDP-B review for the instrument development effort in November 2018.

In November 2019, NEOCam was retired and the NEO Surveyor was directed to begin formulation efforts.  It became a directed mission with planetary defense objectives only.  The NEO Surveyor directly addresses the 2005 Congressionally mandated George E. Brown, Jr. Near-Earth Object Survey Act (PDF) and the 2010 National Research Council report “Defending Planet Earth: Near-Earth-Object Surveys and Hazard Mitigation Strategies.”

The NEO Surveyor has a flight segment, the NEO Surveyor, and a ground segment, the NEO Surveyor Investigation System.  The NEO Surveyor Project will design, build, test, and operate these two systems together optimized in sensitivity, observation cadence, and data analysis pipeline to find and characterize these potentially hazardous objects.  NEO Surveyor is a Category 2 mission per NASA Procedural Requirements (NPR) 7120.5E and Risk Classification C per NASA Program Directive (NPD) 8705.4.  

The biggest difference between NEOCam and NEO Surveyor, besides the new focus on planetary defense, is that NEO Surveyor added University of Arizona as a technical partner.  Dr. Amy Mainzer is now at the University of Arizona and is the NEO Surveyor Survey Director.  Dr. Mainzer leads the UA team, who is responsible for Focal Plane Mosaic work, the Investigation Team and the NEO Surveyor Investigation Software Suite, and overall NEO Surveyor project management.

The NEO Surveyor Mission consists of a single scientific instrument: a 50 cm diameter telescope operating at two heat-sensing infrared wavelengths that are capable of detecting even the dark asteroids that are hardest to find. 

After launch, the NEO Surveyor will carry out a five-year baseline survey to find at least 2/3 of the near-Earth objects larger than 140 meters. These are the objects large enough to cause major regional damage in the event of an Earth impact. By using two heat-sensitive infrared imaging channels, NEO Surveyor can—and will—make accurate measurements of NEO sizes and gain valuable information about their composition, shapes, rotational states, and orbits. See the complete set of mission requirements.

NEO Surveyor employs an innovative observation strategy to independently discover new asteroids and comets and determine their orbits with enough accuracy to allow them to be found again.  NEO Surveyor is designed to find >2/3 of NEOs larger than 140 meters in 5 years, making significant progress toward meeting the U.S. Congress’s mandate to NASA to find >90% of all NEOs larger than 140 m in diameter.  The >90% number is a mission goal to be achieved in 10-12 years.

Infrared light can be used both to tell temperature and find warm objects that don’t reflect much visible light, like asteroids.  The visible light image on the left shows light reflecting off the person and the coffee cups, but the infrared image on the right reveals the heat that both emit. Where the infrared light is brighter, the temperature of the person is warmer. Image credit: JPL/Caltech.

Like NASA’s WISE mission (which was delivered on cost and on schedule according to the March 2011 GAO report), NEO Surveyor will be built and tested by competitively-selected industrial contractors in order to ensure the lowest cost and highest value to taxpayers. NEO Surveyor’s major contractors include Ball Aerospace, Space Dynamics Laboratory (SDL), and Teledyne Imaging Sensors.  Led by the Survey Director (SD), NEO Surveyor’s three major partners, University of Arizona, JPL, and Caltech/IPAC, will provide project systems engineering, manage the contracts for the spacecraft bus, payload, and science data processing, provide the mission operations system, and provide overall project management. The SD is supported by the NEO Surveyor Investigation Team, who is integrally involved at every stage of NEO Surveyor’s development, from requirements definition, design, fabrication, and testing to launch, in-orbit checkout, flight operations, and data analysis, ensuring that the instrument is optimized to meet the mission’s survey objectives.