Mission to bring back asteroid samples

September 2nd, 2016, Published in Articles: EE Publishers, Articles: EngineerIT


What looks like a giant mosquito punching its proboscis deep into the surface of asteroid Bennu is in fact NASA’s latest spacecraft that will help scientists investigate how planets formed and how life began, as well as improve the understanding of asteroids that could impact Earth.

OSIRIS-REx will travel to near-Earth asteroid Bennu on a sample return mission. Credits: NASA

OSIRIS-REx will travel to near-Earth asteroid Bennu on a sample return mission. Credits: NASA

The origins, spectral interpretation, resource identification, security-regolith explorer (OSIRIS-REx) spacecraft will travel to the near-Earth asteroid Bennu and bring a sample back to Earth for intensive study.

Bennu is in an Earth-crossing orbit that circles the sun every 1,2 years with an orbital velocity over 28 km/s.  Bennu approaches the Earth every six years. At the time of its discovery in 1999 Bennu came within 2,2-million km of the Earth (~5,7 times the average distance to the moon). The closest approach is predicted to occur in 2135 when Bennu will fly 300,000 km over the surface of the Earth, well inside the orbit of the moon.

At the time of its discovery in 1999 Bennu came within 2.2 million kilometres of the Earth

At the time of its discovery in 1999 Bennu came within 2,2-million km of Earth.

Bennu also gets very far away from Earth. In a single orbit Bennu travels over a billion km around the sun. At its furthest point it is over 340-million km away from Earth. When OSIRIS-REx is at Bennu it will take over 18 minutes for a signal transmitted from the Earth to reach the spacecraft and another 18 minutes for the spacecraft signal to be transmitted back to Earth.

The 2,110 kg fully-fuelled spacecraft will launch aboard an Atlas V 411 rocket during a 34-day launch period that began on 8 September 2016 and will reach its asteroid target in 2018.

Once in space, OSIRIS-REx will perform a series of deep space manoeuvres, changing velocity by 0,52 km/s. These manoeuvres, combined with an Earth-gravity assist one year after launch, will send OSIRIS-REx on a trajectory to rendezvous with Bennu.

An asteroid rendezvous requires not only being in the same place at the same time but also moving at the same speed and in the same direction. OSIRIS-REx will basically be formation flying with Bennu during the asteroid encounter.

After a careful survey of Bennu to characterise the asteroid and locate the most promising sample sites, OSIRIS-REx will collect between 60 to 2,000 gr of surface material with its robotic arm and return the sample to Earth via a detachable capsule in 2023.

OSIRIS-REx has five instruments to explore Bennu:

  • OSIRIS-REx camera suite (OCAMS) – a system consisting of three cameras provided by the University of Arizona, Tucson, will observe Bennu and provide global imaging, sample site imaging, and will witness the sampling event.
  • OSIRIS-REx laser altimeter (OLA) – a scanning LIDAR (light detection and ranging) contributed by the Canadian Space Agency will be used to measure the distance between the spacecraft and Bennu’s surface, and will map the shape of the asteroid. To create these 3-D models, OLA uses LiDAR. It is similar to radar, but uses light instead of radio waves to measure distance. OLA will emit infrared laser pulses toward the surface of Bennu as the spacecraft moves around the asteroid. The laser pulses reflect back from the surface to a detector. The team will measure the time difference between outgoing and incoming pulses to calculate the distance between the spacecraft and Bennu.
  • OSIRIS-REx thermal emission spectrometer (OTES) – an instrument provided by Arizona State University in Tempe that will investigate mineral abundances and provide temperature information with observations in the thermal infrared spectrum.
  • OSIRIS-REx visible and infrared spectrometer (OVIRS) – an instrument provided by NASA’s Goddard Space Flight Centre in Greenbelt, Maryland and designed to measure visible and infrared light from Bennu to identify mineral and organic material.
  • Regolith X-ray imaging spectrometer (REXIS) – a student experiment provided by the Massachusetts Institute of Technology (MIT) and Harvard University in Cambridge, which will observe the X-ray spectrum to identify chemical elements on Bennu’s surface and their abundances.

The OSIRIS-REx sample return capsule (SRC) is fitted with a heat shield and parachutes in which the spacecraft will return the asteroid sample to Earth, all provided by Lockheed Martin.

Goddard provides overall mission management, systems engineering, and safety and mission assurance for OSIRIS-REx. Lockheed Martin Space Systems built the spacecraft. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. OSIRIS-REx is the third mission in NASA’s New Frontiers Programme.


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