March 2024

This month’s space science mission article presents three NASA missions that use Teledyne’s image sensor products. The missions discussed are:

• The OSIRIS-REx asteroid sample return mission
• The Lucy mission that will study Jupiter’s Trojan asteroids
• The Near-Earth Object Surveyor mission that will find and study large asteroids that could endanger the Earth

OSIRIS-REx Asteroid Sample Return Mission

Asteroids are composed of the raw material that formed the solar system and a pristine sample of an asteroid is a time capsule from the birth of the solar system. NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) is the most ambitious asteroid sample return mission ever attempted.

The OSIRIS-REx mission was launched from the Kennedy Space Center (Florida) on September 8, 2016 and arrived at the asteroid 101955 Bennu on December 3, 2018.

Bennu is a very dark object with 4% albedo (reflectivity), similar to fresh asphalt or dark wet soil. Bennu is much darker than it appears in this image for which the image contrast has been adjusted to better reveal surface features. Bennu is covered by boulders, the largest of which – visible in partial shadow in lower right – is about 76 meters (250 feet) across.

Bennu is a carbonaceous near-Earth asteroid that is 592 meters wide and is a Potentially Hazardous Asteroid, with a 1 in 2,700 chance of hitting the Earth between 2175 and 2199. During January 2019 – June 2020, OSIRIS-REx orbited and mapped Bennu’s surface to identify the best area from which to retrieve a sample to bring back to Earth. Teledyne had a major role in the instruments on OSIRIS-REx, providing the sensors for three of four science instruments:

• OCAMS (OSIRIS-REx Camera Suite): Teledyne’s CCD detectors were used in three visible light cameras that produced most of the images taken of Bennu. OCAMS mapped the entire asteroid surface and provided detailed imagery of the potential sample sites. One of the cameras recorded the entire sampling event during the touch-and-go maneuver. (“Touch-and-go” means that OSIRIS-REx never fully landed. The spacecraft slowly approached Bennu and touched the surface briefly to collect the sample.)
• OLA (OSIRIS-REx Laser Altimeter): Teledyne’s scanning lidar (light detection and ranging) systems emit laser pulses and measure the light reflected from the surface. Precise measurement of the time between sending the outgoing pulse and the sensed return provided high resolution topography of the asteroid surface as shown in the colorful animated GIF below. The lidar measurements enabled the mission team to program the spacecraft to adjust its speed for the touch-and-go maneuver for sampling and avoid collision with large boulders. The OLA lidar system was provided by the Canadian Space Agency.
• OVIRS (OSIRIS-REx Visible and Infrared Spectrometer): This instrument measured over 200 colors of visible and infrared light spanning 0.4 to 4.3 micron wavelengths using a Teledyne H1RG focal plane array. Since every chemical and mineral has a unique spectral signature, OVIRS provided spectral maps that identified mineral and organic material on the asteroid.

The combination of information from OCAMS, OLA, and OVIRS was used to select the site to sample the asteroid.

During the mapping of Bennu, OSIRIS-REx found six boulders ranging in size from 1.5 to 4.3 meters (5 to 14 feet) that clearly came from another asteroid. These boulders were up to 10 times brighter than their surrounding and were made of an igneous rock call pyroxene. Using light reflected off the boulders, the OSIRIS-REx visible and infrared spectrometer (OVIRS) gave scientists a sense of the chemical composition. Scientists think that Bennu most likely acquired these bright boulders from a fragment of the asteroid Vesta that collided with the parent body of Bennu. The image below shows the bright boulders on Bennu.

On October 20, 2020, OSIRIS-REx touched down and successfully retrieved a sample that exceeded the mission’s minimum success criterion of 60 grams (2.1 ounces) of material. The sample collection is shown in the video below.

OSIRIS-REx departed Bennu in May 2021 and landed the sample return capsule on September 24, 2023 at the U.S. Air Force Test and Training Range in Utah.

Within the sample return capsule (SRC), the asteroid sample was sealed in a sampler head named TAGSAM (Touch-And-Go Sample Acquisition Mechanism). To protect the sample, after removal from the SRC, NASA placed the TAGSAM in a specialized glovebox that has a flow of nitrogen to prevent contamination. Before attempting to open the TAGSAM, NASA recovered 70.3 grams (2.48 ounces) of material from the outside of the sample cannister, already surpassing the mission’s goal of bringing at least 60 grams of material back from Bennu.

However, for three months NASA struggled to open the TAGSAM because two of the 35 fasteners on the canister could not be removed by tools approved for use in the glovebox. NASA engineers developed new clean room tools and NASA was able to open the two stubborn fasteners on January 10, 2024. The first image of the material inside the canister is shown below. The total material that was brought back to Earth was 121.6 grams, about double the mission’s goal. A portion of this material is being shared with scientists worldwide for detailed study. The rest of material will be stored for use in future investigations when new diagnostic equipment is developed or for comparison with future asteroid sample return missions.

Meanwhile, after OSIRIS-REx dropped off the TAGSAM at Earth, the spacecraft was redirected to visit and study the near-Earth asteroid Apophis. The 340-meter wide Apophis will make an extremely close pass to the Earth on April 13, 2029, coming within 31,000 km (19,000 miles), closer than geostationary satellites. The extended mission, named OSIRIS-APEX (APEX = Apophis Explorer), will rendezvous with Apophis shortly after its closest approach to Earth. For the following 18 months (during 2029 – 2030), OSIRIS-APEX will examine Apophis in great detail, using its thrusters to disturb Apophis’s surface and expose subsurface material for spectral measurements.

NASA Lucy Mission

On October 16, 2021, NASA launched the Lucy mission to study the Trojan asteroids that co-orbit with Jupiter. Lucy is humankind’s first space mission to study the Trojans. The mission takes its name from the fossilized human ancestor (called “Lucy” by her discoverers) whose skeleton provided unique insight into humanity’s evolution. Likewise, the Lucy mission will revolutionize our knowledge of planetary origins and the formation of the solar system.

The Lucy mission will be a 12-year journey to 8 asteroids, 2 main belt asteroids, and 6 Jupiter Trojans. The flight path, shown in the figure below, uses the Earth’s gravity for gaining the velocity to travel to the outer solar system. Two of the instruments on the Lucy mission use Teledyne’s detectors.

• L’Ralph is a panchromatic and color visible imager (0.4-0.85 μm wavelengths) and an infrared spectroscopic mapper (1.0-3.6 μm wavelengths) that uses a Teledyne H2RG infrared detector. L’Ralph will be used to measure silicates, ices, and organics at the surface of the asteroids.
• L’LORRI is a high resolution visible imager using a Teledyne CCD47-20 that will provide the most detailed images of the surfaces of the Trojans.

On its way to the Trojan asteroids, Lucy was tasked to image a small 780-meter (2,600 feet) main belt asteroid to test the spacecraft’s autonomous ability to track and image its asteroids targets. On November 1, 2023, Lucy observed Dinkinesh and scientists were surprised to find that Dinkinesh was a binary asteroid for which the satellite of the main asteroid is a contact binary.

After a brief encounter with the inner edge of the asteroid belt, Lucy is now heading back toward the Earth for a gravity assist in December 2024. The Earth flyby will give Lucy enough speed to travel back through the main asteroid belt, observing the asteroid Donaldjohanson in 2025, and arriving at the L3 Trojan asteroids in 2027.

NASA Near Earth Object Surveyor Mission

Asteroids have the potential to cause catastrophic impacts with the Earth but we have not yet found all large near-Earth objects, some of which may have the potential to collide with the Earth. To fill the gaps in our knowledge, NASA is funding the Near-Earth Object Surveyor (NEO Surveyor) mission. The primary purpose of the mission is to find dangerous asteroids before they have a chance to hit the Earth. If an asteroid is detected several years before a potential collision, the asteroid’s orbit could be modified to miss the Earth. The technology for asteroid deflection is not yet mature and will need to be developed in parallel with the NEO Surveyor mission.

The NEO Surveyor will advance NASA’s planetary defense efforts to discover and characterize most of the potentially hazardous asteroids and comets that come within 30 million miles of Earth’s orbit. These are collectively known as near-Earth objects, or NEOs.

The red dots depict the positions of asteroids measured by NEO Surveyor in a series of images. The asteroids will not be spatially resolved by the small 50 cm telescope – even the largest asteroids will subtend less than one pixel. NEO Surveyor will use the asteroid’s brightness in mid-wave infrared (MWIR) and long-wave infrared (LWIR) bands to determine the asteroid size. An asteroid’s motion (measured against the “fixed” background stars) over a series of images is used to determine the asteroid orbit and whether there is potential for collision with the Earth.

In comparison with JWST and other astronomy missions, the NEO Surveyor has a modest sized telescope, only 50 cm in diameter. Making NEO Surveyor unique are:

• its wide field of view (11.56 square deg);
• radiative cooling to keep the LWIR (10.5 µm cutoff) H2RG focal plane arrays (FPAs) operating at a temperature of ∼40K;
• its observing position at Lagrange Point 1 (L1), the Sun–Earth Lagrange point that is 1.5 million km from the Earth in the direction of the Sun. L1 is the best place from which to find and characterize NEOs.

NEO Surveyor will simultaneously image the same field of view (FOV) in two bands, MWIR (4–5 µm) and LWIR (6–10 µm) using two 1×4 mosaics of H2RGs (two 2K×8K mosaics, total of 33 million pixels). Each H2RG will be operated by a SIDECAR ASIC module, a new package design developed for NEO Surveyor based on lessons learned from the European Space Agency’s Euclid mission. The figure below shows the H2RG, CAD drawing of the SIDECAR ASIC module, and a prototype of the 1×4 H2RG mosaic mount. Teledyne’s H2RG and SIDECAR ASIC module deliveries to NEO Surveyor will be completed in early 2024.

Infrared light is much better than visible light for measuring the size of asteroids because:

• Visible light imaging of asteroids detects the sunlight reflected by the asteroid. A small highly reflective object appears to be the same brightness as a large, low reflectivity object.
• MWIR and LWIR imaging is detecting light that is emitted by the asteroids, which is a function of the temperature of the asteroid. Since asteroid temperatures are similar, the combination of MWIR and LWIR measurements with knowledge of the asteroid type provides a good estimate of asteroid size.

After launch in September 2027, NEO Surveyor will carry out a five-year baseline survey to find near-Earth objects larger than 140 meters (460 feet). These objects are large enough to cause major regional damage in the event of an Earth impact. Using MWIR and LWIR bands, NEO Surveyor will make accurate measurements of NEO sizes and gain valuable information about their composition, shapes, rotational states, and orbits.