Introduction time, it finally landed on the
The Near Earth Asteroid Rendezvous – Shoemaker (NEAR) was launched in 1996. It was designed at Johns Hopkins University. The spacecraft was named in respect of the great planetary scientist known as Eugene Shoemaker. It was a computerized space explorer aimed at helping to conduct a study of asteroid Eros from a close distance. After the robot orbited around Eros from a close distance for some time, it finally landed on the asteroid in 2001 (Stathopoulos para. 1).
The spacecraft explorer was aimed at reporting back on the features of the Eros. These included the magnetic field properties of the asteroid, the kind of minerals available and the composition of the asteroid. Other objectives of the project included understanding the regolith features, the state of its spin, effects of solar wind on the asteroid and probable current activity.
This could have made it possible for National Aeronautics and Space Administration (NASA) to understand the asteroid well plus know its relationship to comets and other heavenly bodies (National Aeronautics and Space Administration Marshall Space Flight Centre para. 1-3).
The NEAR Shoemaker. Source: http://nssdc.gsfc.nasa.gov/planetary/near.html
The journey to asteroid Eros
After its launch, the spacecraft entered its first cruise stage. This stage had limited activity and only took a few days before it traversed across asteroid 253 Mathilde which is 61km in diameter. While flying at about 1200km from Mathilde, NEAR was able to record and send back about 500 images that it could capture on the surface of Mathilde. The spacecraft also sent back information about the gravitational data making it possible for the mission controllers to calculate the diameter and mass of asteroid Mathilde (Stathopoulos para. 2).
Failure of the first attempt
The spacecraft was expected to undergo four rendezvous burns. To ensure that this worked as planned, the spacecraft underwent a test in December 20, 1998. The first burn cycle was launched but abandoned immediately. Subsequently, the spacecraft got into safe mode and started going up.
During this glitch, the spacecraft’s thrusters were fired many times stretching the spacecraft’s propellant by 29kgs. The spacecraft’s battery got drained as well as its solar orientation interrupted. The error almost led to total loss of the spacecraft. It took 24 hours before the mission control team could spot the spacecraft (Williams para. 2).
During this period, no communication was possible between NEAR and the control team. Till now, it has never been established the root cause of this glitch. However, there are those who blame the error to software malfunction while others blame the mission control team (Williams para. 4). It was expected that after the four burns were completed, orbit insertion burn would follow. However, failure of the first burn and subsequent loss of communication between the mission control team and the spacecraft rendered the procedure unfeasible.
A new procedure had to be put in place immediately to ensure that the project continued without further interruptions. This made it possible for NEAR to draw closer to Eros and fly by it at a distance. Moreover, it was possible to capture images on the surface of Eros using a camera and record data regarding the asteroid’s gravitational action.
On January 3, 1999 a thruster burn was performed to synchronize the orbital speed of the spacecraft with that of the asteroid. It was later followed by another burn that facilitated in fine-tuning the path of the spacecraft (Stathopoulos para. 3).
Image of Eros taken by NEAR. Source: http://neo.jpl.nasa.gov/missions/near.html
On 14 February, 2000 the mission control team managed to conduct an orbital insertion. This was after the spacecraft had gone around Eros for thirteen months tracing a trajectory that closely matched that of the asteroid. Before orbital insertion was conducted, the team reduced the orbiting speed of NEAR from 19.3 to 8.1 m/s ((Stathopoulos para. 4).
Later the speed was slightly increased to 9.9 m/s. To ensure that the spacecraft did not come into collision with other satellites orbiting the asteroid, the teamed conducted a search to ensure that there are no satellites. No satellite was found. With time, the spacecraft’s orbit was reduced drawing it closer to the asteroid which eventually led to it landing on Eros.
Orbits and landing
From January 24 2001, the spacecraft started drawing closer to the asteroid starting by orbiting at 6 km away from Eros. By January 28, the spacecraft was 3km away from the asteroid. The spacecraft then gradually descended towards the surface of the asteroid and landed on 12 February the same year (Stathopoulos para. 4-6). The landing was safe leaving the spacecraft in sound condition; to the surprise of the controllers.
When on the surface, its gamma-ray spectrometer was used in collecting information about the asteroid’s composition. This gave back a more accurate information than the one that had been collected when NEAR was orbiting around Eros.
The last data signals to be received from the spacecraft reached the mission control team on February 28, 2001. The spacecraft was later shut down. An attempt by the control team to communicate with NEAR on December 10, 2002 did not bear fruits. This was attributed to high temperature that was experienced in Eros during the check out (Yeomans para. 1-4).
Image taken as NEAR descended towards Eros’ surface. Source: http://discovery.nasa.gov/near.cfml
National Aeronautics and Space Administration Marshall Space Flight Centre. “NEAR.” 2011. Web. 22 November 2011.
Stathopoulos Vic. “Near Shoemaker.” 2011. Web. 22 November 2011.
Williams, David R. “NEAR Flyby of Asteroid 253 Mathilde.” December 18, 2001. Web. 22 November 2011.
Yeomans, Don. “NEAR-Earth Asteroid Rendezvous (NEAR).” 2011. Web. 22 November 2011.