FAQ: Spot the Spacecraft

On Sept. 22, 2017 at 12:52 p.m. EDT (16:52 UTC), NASA’s OSIRIS-REx spacecraft will fly past Earth and use the planet’s gravity to slingshot itself toward asteroid Bennu in a maneuver known as an Earth Gravity Assist (EGA). Observatories and astronomers with their own equipment are invited to take images of OSIRIS-REx as it approaches and retreats from its closest position over Earth—approximately 11,000 miles (17,000 km) above the planet’s surface.

The mission will collect images of OSIRIS-REx taken by Earth-based observers around the world during this period – approximately Sept. 10-23, depending on location and local conditions. See below for more details about when and where you can observe the spacecraft and how to submit your images.


Who may participate?

Anyone with the necessary equipment.

What equipment do I need?

Observers will need a telescope (preferably 8 inches or larger) and a camera.

When should I observe?

September 10-23, 2017. Large telescopes may be able to see the spacecraft as early as Sept. 10; most amateur telescopes will not be able to capture it until Sept. 18. The spacecraft’s closest approach will be approximately 17,000 km over Antarctica and Australia in daylight. Observers in both hemispheres may be able to see the spacecraft during approach until a few hours before closest flyby.

Where will OSIRIS-REx appear in the sky?

For many observers, the spacecraft will appear in the constellations of Cetus and Pisces. Use the HORIZONS database from NASA’s Jet Propulsion Laboratory to look up specifics for your observing location. Use “ORX” for the target body, enter your location, and enter desired observing dates and time intervals to retrieve Right Ascension and Declination.

How bright will the spacecraft be?

OSIRIS-REx will not be visible to the naked eye. It is difficult to estimate the precise orientation of reflective surfaces, so visual magnitudes are uncertain and depend on many factors (spacecraft distance, orientation with respect to the Sun, altitude, sky conditions, brightness of the Moon, etc.). The best estimates are:

  • Sept. 10: 20th -23rd magnitude
  • Sept. 15: 18th – 22nd magnitude
  • Sept. 18: 17th – 21st magnitude
  • Sept. 21: 14th – 18th magnitude
  • A few hours before closest approach: 9th – 11th magnitude

What exposure times should I use?

The lateral motion of the spacecraft is expected to be small during Earth approach. Use the same exposure times that would be appropriate for a slow-moving asteroid. For some setups, this means 30 seconds or less. Start with “long” exposures and shorten if needed to reduce any smearing from the spacecraft motion and Earth’s rotation. Or, just take one very long exposure of the sky to capture OSIRIS-REx among star trails. The spacecraft will be moving much faster in the hours leading up to EGA so shorter exposures may be required.

What kind of images are needed?

Images of any format are accepted, but FIT or FITS files are preferred.

How do I submit images?

Upload them via the form on the OSIRIS-REx mission website.

What file names should I use?

The suggested image file name is in the format: Observer_OREx_YYYYMMDD_HHMMSS.FITS (Example: JSmith_OREx_20170922_041510.FITS)

How will the images be used?

Selected images may be included in press releases, posted to social media or the mission website. Members of the mission team may also use them for scientific purposes.

I have more questions.

Contact us at: socialmedia@orex.lpl.arizona.edu

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