OSIRIS-Rex

Source: NASA, [n.d.] [1]

MISSION

The Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer, or OSIRIS-REx, is a NASA mission in which a spacecraft travels to a near-Earth asteroid to gather samples to help scientists investigate how planets formed and how life began, as well as improve our understanding of asteroids that could impact Earth. The mission, launched September 8, 2016, is the first U.S. mission to return samples from an asteroid to Earth. OSIRIS-REx began the approach phase to the near Earth asteroid Bennu, a carbon-rich asteroid, in August 2018, and is scheduled to arrive at Bennu on December 3, 2018. After arrival, the spacecraft will spend six months mapping the asteroid’s surface, and scientists will choose the location from where the spacecraft will extract a sample. Once within close range, a robotic arm will extend to collect at least 60 grams (2.1 ounces) and up to 2 kilograms (4.4 pounds) of sample of material for return to Earth in 2023. [2]

Source: NASA, 2014 [3]

OSIRIS-REx is a component of NASA’s New Frontiers program. New Frontiers tackles specific solar system exploration goals identified as top priorities by NASA and the planetary space community. These high-priority scientific goals focus on the exploration of Venus, Jupiter, the south polar region of the Earth’s Moon, Pluto and other Kuiper Belt objects, and comets. NASA solicits proposals to the New Frontiers program from researchers affiliated with universities and research institutions; who in turn select a team consisting of industry, small businesses, government laboratories and universities. The principal investigator is responsible for the success of the project, which must cost less than $850 million, by assuring that cost, schedule and performance objectives are met. [4]

SIGNIFICANCE

BACKGROUND

Asteroids are remnants left over from the formation of the solar system more than 4.5 billion years ago. [5] They contain the basic elements like carbon that were building blocks for the terrestrial planets, including Earth. The presence of complex organic molecules in meteorites discovered on Earth lead scientists to believe that asteroid impacts may have seeded Earth with the building blocks of life. Therefore, scientists wish to better understand their chemical and physical nature, distribution, formation, and evolution in order to learn more about planet formation and the origin of life. [6]

About once every 10,000 years, rocky asteroids larger than 100 meters collide with Earth. In addition to local damage at the point of impact, a small asteroid collision could cause tidal waves that can inundate low lying coastal areas. A much larger asteroid with a diameter larger than one kilometer could cause global disaster. Large asteroid collisions only occur once every several hundred thousand years or so but could affect the Earth’s ecosystem more profoundly as impact debris could spread through Earth’s atmosphere and block sunlight, cause acid rain, and rain heated debris on Earth’s surface. [7] Scientists believe that a large asteroid or comet strike is responsible for the conditions that led to the extinction of the dinosaurs 65 million years ago. [8]

A Near Earth Object (NEO) is an asteroid or comet whose orbit around the Sun takes it close to Earth’s orbit. NEOs that pass within about one-third the average distance of Earth to the Sun hold the potential to collide with Earth. The vast majority of these dangerous NEOs are asteroids, referred to as Near-Earth Asteroids (NEAs). Any asteroid that comes within 4.6 million miles of Earth with a diameter greater than 500 feet is considered to be a Potentially Hazardous Asteroid (PHA). There are over 1,300 PHAs – objects at least 150 yards (about 140 meters) across with a very small chance of impacting us someday because their orbital paths take them close to Earth's orbit. [9] Not all PHAs will impact Earth; rather, this designation indicates that the asteroids hold the possibility for such a threat. NASA can more accurately determine if these PHAs threaten the planet through monitoring and tracking their orbits over time. [10]

It should also be noted that NEOs pose not just an impact threat to the Earth, but an opportunity to gain precious resources. Asteroids contain raw materials that could one day be harvested and used to build spacecraft structures; comets contain life-sustaining water and organic molecules, and water from comets could be split to form liquid hydrogen and oxygen, ingredients in rocket fuel. These resources could enable us to explore the solar system. It has been estimated that the mineral wealth in the belt of asteroids between the orbits of Mars and Jupiter would be equivalent to about 100 billion dollars for every person on Earth today. [11]

In 1998, the U.S. Congress passed legislation mandating that NASA discover 90 percent of Near Earth Objects (NEOs) with a diameter of 1 kilometer or greater within 10 years. This legislation, known as the Spaceguard Survey, was followed by a second mandate in 2005, the George E. Brown, Jr. Near-Earth Object Survey Act. This called for NASA to detect 90 percent of NEOs 140 meters in diameter or greater by 2020. [12] There are thought to be approximately 1000 NEAs larger than one kilometer and around 15,000 NEAs larger than 140 meters. [13] As of September 2018, more than 18,740 Near Earth Objects (NEOs) had been discovered. Over 90 percent of NEOs greater than one kilometer have been discovered. Researchers are now working towards the goal finding 90 percent of the NEO population larger than 140 meters. [14]

OSIRIS-REX MISSION

An asteroid’s path, and potential to collide with Earth, is affected by more than the gravitational pull of the sun and planetary bodies in the solar system. One of the smaller forces continuously acting on an asteroid’s orbit is the Yarkovsky effect, a minute force on an asteroid that occurs when the asteroid absorbs heat energy from the sun and re-radiates that heat in a different direction. This occurs as the asteroid tumbles through space, with one side being heated and then cooled as it turns away from the sun. The strength of the Yarkovsky effect is variable depending on the asteroid’s size, shape and composition. One focus of the OSIRIS-REx mission is to measure the Yarkovsky effect on a NEO in order to better predict its orbit behavior. [15]

Scientists have chosen the asteroid called Bennu (formerly designated as 1999 RQ36) as the destination for OSIRIS-REx. Bennu is about 1,900 feet in diameter (roughly the size of six football fields). It was chosen for two major reasons: Bennu is one of the most accessible carbonaceous NEAs; and, it has a relatively high probability of impacting Earth, a one in 1,800 chance of hitting Earth by the 22nd century. [16] Scientists expect this asteroid, which has orbited the sun since the solar system’s infancy, could tell us more about the formative years of our solar system. The asteroid is likely rich in carbon, one of the organic molecules necessary for life on Earth that has already been discovered in other meteorites and comets. In addition, scientists will be able to learn more about asteroid orbital behavior that will assist in determining asteroid impact threats and create deflection strategies. [17]

TEAM

The OSIRIS-REx team consists of university researchers, NASA personnel, and industry members. Dr. Dante Lauretta, from the University of Arizona, is OSIRIS-REx’s principal investigator. NASA’s Goddard Space Flight Center, located in Greenbelt, Maryland, manages the project. [18] For a full listing of team members and affiliations, click here.

ACADEMIC MEMBERS

University of Arizona

  • Coordinates the Science Team and performs science operations
  • Builds and operates the OSIRIS-REx Camera Suite (OCAMS) [19]

 Arizona State University

  • Provides the OSIRIS-REx Thermal Emission Spectrometer (OTES) [20]

Other Team Members

GOVERNMENT MEMBERS

Goddard Spaceflight Center

  • Provides project management to the OSIRIS-REx mission
  • Provides science expertise and system engineering through NASA personnel
  • Produces and manages the OSIRIS-REx Visible and IR Spectrometer (OVIRS)

Johnson Space Center

  • Curates the samples that will be returned from 1999 RQ36

Canadian Space Agency

  • Contributes to the OSIRIS-REx Laser Altimeter (OLA)

Japan Aerospace Exploration Agency

  • Collaborative efforts with Japan’s own NEA sampling mission, Hayabusa 2

INDUSTRY MEMBERS

Lockheed Martin Space Systems is a development partner on OSIRIS-REx. They are responsible for:

  • Building the spacecraft on which all instruments will be mounted. [21]
  • Producing the asteroid sampling system and the sample return capsule
  • Operating the spacecraft from its Mission Support Area from launch through sample return [22]

KinetX

  • Primary provider of spacecraft navigation and mission design including trajectory optimization, orbit determination and propulsive maneuver design [23]

Southwest Research Institute

  • Contributes to the OSIRIS-REx Thermal Emission Spectrometer (OTES) [24]

TECHNOLOGY

OSIRIS-REx will further refine our understanding of the Yarkovsky effect by providing a precise measurement of Bennu’s orbit. OSIRIS-REx will arrive at Bennu in 2018 and orbit the asteroid until 2021, providing measurements at least twice as precise as what is available now. The science team working on OSIRIS-REx plan to use this information to estimate the Yarkovsky effect on other asteroids. [25]

Scientists already know that the asteroid Bennu has a density of about one gram per cubic centimeter, about half as solid as rock. Therefore, the asteroid may be a loose collection of rocks and dust held together by gravity. OSIRIS-REx will utilize visible light and infrared spectrometers to measure the composition of Bennu. In addition, the spacecraft will collect data during orbit of the asteroid, creating a gravitational map showing the internal structure of Bennu. [26]

SPACECRAFT

The OSIRIS-REx spacecraft was built by Lockheed Martin Space Systems.

  • The craft is in the shape of a cube, approximately 2 meters (6.6 feet) on each side.
  • Solar arrays stretch 8.5 square meters (91 square feet). Energy captured from the sun charges lithium-ion batteries, powering the OSIRIS-REx spacecraft and instruments.
  • OSIRIS-REx utilizes the Touch-and-Go sampler (TAGSAM), an articulated arm with a sampler head that can collect regolith from the asteroid’s surface. TAGSAM will slowly approach Bennu and use nitrogen gas to push the sample into the collecting head. There is enough nitrogen gas to support three collection attempts. Spacecraft inertia change will verify sample collection.
  • A sample return capsule (SRC) on the outside of the spacecraft will be used to return at least 60 grams of asteroid sample to Earth in 2023. The SRC is the same as used in the Stardust mission (1999-2006). [27]

INSTRUMENTS

OSIRIS-REx is outfitted with five instruments for remote sensing or scanning of the surface of Bennu to map and establish what makes up the asteroid, including the distribution of elements, minerals, and organic material. [28]

Source: NASA/University of Arizona [29]

OSIRIS-REx Camera Suite (OCAMS)

The OSIRIS-REx Camera Suite (OCAMS) provides global image mapping, sample-site characterization, and millimeter resolution imaging. OCAMS was built by the University of Arizona, and consists of three cameras:

  • PolyCam, an 8-inch telescope that acquires the asteroid’s position from 2 million km away, and images it at high resolution from closer ranges.
  • MapCam will map the asteroid in four colors, search for satellites and outgassing plumes, and image the sample site in high resolution.
  • SamCam is situated near the TAGSAM and will continuously document sample acquisition.

These three cameras provide overlapping capabilities in navigation, mapping, reconnaissance, and sample-collection documentation, fulfilling all mission and science imaging requirements.

OSIRIS-REx Laser Altimeter (OLA)

OLA is a scanning and LIDAR (Light Detection and Ranging) instrument that will provide high-resolution topographical information about Bennu, as well as support other instruments and navigation and gravity analyses. OLA will emit laser pulses at the surface of Bennu, which will reflect back from the surface and return a portion of the laser pulse to the LIDAR detector. The distance of the spacecraft and the surface of Bennu can be computed using the speed of light by carefully measuring the time difference between the outgoing pulse and the incoming pulse.

OSIRIS-REx Visible and IR Spectrometer (OVIRS)

OVIRS is a spectrometer that will measure visible and infrared light from Bennu. OVIRS is sensitive from blue through near-infrared wavelengths. OVIRS will split the light received from Bennu into its component wavelengths, and can identify different chemicals as they each have unique spectral signatures. OVIRS will provide spectral maps that identify mineral and organic material globally and of candidate sample sites, as well as gather local spectral information of candidate sample sites.

OSIRIS-REx Thermal Emission Spectrometer (OTES)

OTES provides mineral and thermal emission spectral maps of the asteroid. OTES collects thermal infrared spectral data from Bennu to create global and local spectral maps. The instrument will be able to detect the presence of silicate, carbonate, sulfate, phosphate, oxide, and hydroxide minerals. OTES is based on the Mini-TES on the Mars Exploration Rover and the TES on the Mars Global Surveyor orbiter.

REgolith X-ray Imaging Spectrometer (REXIS)

REXIS is an instrument that will be used to collect, and image fluorescent X-rays emitted by Bennu, thereby providing spectroscopic information regarding the chemical makeup of the asteroid regolith and the distribution of features over its surface. REXIS is a Student Collaboration Experiment (SCE) between students and faculty at MIT and Harvard University that largely designed, developed, and built the instrument. Over 15 semesters, more than 100 undergraduates and more than 10 graduate students from MIT and Harvard are expected to participate in the REXIS project. Students will handle data analysis of the REXIS X-ray data.

EXPECTED OUTCOMES

Through the OSIRIS-REx mission, scientists hope to gain a better understanding of the Yarkovsky effect, a small force that results from the Sun heating the asteroid and the re-radiation of that energy to space. After orbiting Bennu for three years, the asteroid’s orbit will be measured with at least twice the precision as is currently available to researchers studying asteroids from the ground. This information will be applied to measurements of other asteroids to more precisely estimate their orbital path and risk to Earth. [30]

The mission will also provide crucial experience navigating a spacecraft around an asteroid. An asteroid’s gravitational pull is so weak, it is similar to the push of the sun’s rays on the spacecraft’s solar panels.  The OSIRIS-REx team will generate a set of techniques and technologies to navigate around Bennu that will be applicable to future missions to asteroids. [31]

Artist concept of the OSIRIS-REx spacecraft near asteroid Bennu, NASA Goddard Space Flight Center, 1999 [32]

Updated September 2018 by Diane Meade

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