OSIRIS-REx Asteroid Sampler Completes 1st Engine Firing for Final Approach to Target Bennu

Illustration of NASA’s
OSIRIS-REx spacecraft during a burn of its main engine for arrival at target
Asteroid Bennu in Dec. 2018.  Credit: University
of Arizona
Ken Kremer     SpaceUpClose.com     9 October 2018

FL – NASA’s OSIRIS-REx asteroid sampling spacecraft successfully
completed the first in a series of critical main engine firings in early
October that significantly slowed the probes speed and put it on course for
final approach to target Bennu this December. 
A second firing is on tap just days away for Oct. 15. 

commanded OSIRIS-Rex to carry out the firing known as the first Asteroid
Approach Maneuver (AAM-1) on Oct. 1.  All
appeared to go well but the team need to gather additional and analyze
additional telemetry and tracking to confirm a positive outcome.

“New tracking data confirm that the spacecraft
completed its first Asteroid Approach Maneuver (AAM-1) on Oct. 1, starting the
final approach to Bennu,” officials reported yesterday, Oct. 8.
NASA says the main
engine burn slowed the spacecraft as planned – by a speed of 785.831 miles per
hour (351.298 meters per second) and consumed 532.4 pounds (241.5 kilograms) of

The braking maneuver slowed
the spacecraft’s speed relative to Bennu from approximately 1,100 mph (491
m/sec) to 313 mph (140 m/sec). 

Three more AAMs are scheduled over the next two
months “as the spacecraft prepares to match Bennu’s speed so it can safely
navigate around the asteroid.”

The second maneuver known as AAM-2 is slated
for early next week on Oct. 15. 

As of today with 53 days left until arrival at
OSIRIS-Rex is now less
than 80,500 km (50,300 miles) distant.

OSIRIS-Rex, which stands for the  Origins, Spectral Interpretation, Resource
Identification, Security-Regolith Explorer, has journeyed approximately 1.1
billion miles (1.88 billion km) since its Sept. 8, 2016, launch on a United
Launch Alliance Atlas V rocket.

The one way light time for signals is currently
7.2 minutes.

OSIRIS-Rex counts as NASA’s first
mission to visit a near-Earth asteroid, survey the surface, collect a sample
and deliver it safely back to Earth. 

It is scheduled to arrive at Bennu in about two  months on
Dec. 3, 2018. 

On Aug. 17, 2018 NASA’s OSIRIS-REx
spacecraft obtained the first images of its target asteroid Bennu from a
distance of 1.4 million miles (2.2 million km), or almost
six times the distance between the Earth and Moon. This cropped set of five
images was obtained by the PolyCam camera over the
course of an hour for calibration purposes and in order to assist the mission’s
navigation team with optical navigation efforts. Bennu is visible as a moving
object against the stars in the constellation Serpens.  Credits: NASA/Goddard/University of Arizona

The probe has begun science operations and is
taking images with the cameras to support navigation and science objectives.

Watch this GIF of Bennu

Bennu Brightening as
OSIRIS-REx Approaches.
processed and cropped set of images shows Bennu (in the center of the frame)
from the perspective of the OSIRIS-REx spacecraft as it approaches the
asteroid. During the period between August 17 and October 1, 2018 the
spacecraft’s PolyCam imager obtained this series of 20 four-second exposures
every Monday, Wednesday, and Friday as part of the mission’s optical navigation
campaign.   From the first to the last
image, the spacecraft’s range to Bennu decreased from 2.2 million km to 192,000
km, and Bennu brightened from approximately magnitude 13 to magnitude 8.8 from
the spacecraft’s perspective. Credit: NASA/Goddard/University of Arizona

“From the beginning
of the mission’s science operations on Aug. 17 through AAM-1, PolyCam obtained
optical navigation images (OpNavs) of Bennu on a Monday, Wednesday and Friday
cadence. After AAM-1, PolyCam is taking daily OpNavs as the spacecraft
continues to close in on the asteroid,” NASA reported Oct. 8. 

“This last week the spacecraft’s MapCam camera also began taking
daily Phase Function images. These images support the mission’s science
requirement to measure changes in light reflected from Bennu’s surface as the
Sun illuminates the asteroid across a range of angles. These observations
provide information on Bennu’s albedo and the way light reflects under various
observing conditions.”

OSIRIS-Rex spacecraft in KSC cleanroom prior to
launch. Credit: Ken Kremer/kenkremer.com/spaceupclose.com

The asteroid approach maneuvers are designed to
fly the spacecraft through a precise corridor during its final slow approach to

The final one known as AAM-4 is scheduled for
Nov. 12 and target
OSIRIS-Rex for arrival
on Dec. 3.

“AAM-4 will adjust the spacecraft’s trajectory
to arrive at a position 12 miles (20 km) from Bennu on Dec. 3. After arrival,
the spacecraft will initiate asteroid proximity operations by performing a
series of fly-bys over Bennu’s poles and equator.”
Watch for Ken’s
continuing onsite coverage of NASA, SpaceX, ULA, Boeing, Lockheed Martin,
Orbital ATK and more space and mission reports direct from the Kennedy Space
Center, Cape Canaveral Air Force Station, Florida and Wallops Flight Facility,

Stay tuned here for Ken’s continuing Earth and Planetary science
and human spaceflight news: www.kenkremer.com –www.spaceupclose.com –
twitter @ken_kremer – email: ken at kenkremer.com
Dr. Kremer is a research
scientist and journalist based in the KSC area.

Ken’s photos are for sale and he is available for lectures and outreach events

Ken Kremer

Watch for Ken’s continuing onsite coverage of NASA, SpaceX, ULA, Boeing, Lockheed Martin, Northrop Grumman and more space and mission reports direct from Kennedy Space Center and Cape Canaveral Air Force Station in Florida and Wallops Flight Facility in Virginia. Stay tuned here for Ken's continuing Earth and Planetary science and human spaceflight news. Dr. Kremer is a research scientist and journalist based in the KSC area, active in outreach and interviewed regularly on TV and radio about space topics. Ken’s photos are for sale and he is available for lectures and outreach events.

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