Space · Asteroid Eros · 2001

The Orbiter That Landed Without Landing Gear

The eventual landing was not the original job description.

1. Built to meet an asteroid

NASA's NEAR spacecraft launched in 1996 to study an asteroid at close range. Its main destination was Eros. The mission was designed around observation from space, rather than a conventional landing with legs and a purpose-built surface platform. First, it had to arrive successfully.

The eventual landing was not the original job description.

2. A meeting postponed

A difficult approach manoeuvre in 1998 prevented the planned immediate rendezvous with Eros. The spacecraft flew past instead, collecting observations while the team devised another opportunity. Missing the first appointment did not automatically mean losing the entire mission, provided fuel and navigation could support another attempt.

The asteroid was not going anywhere convenient, so the mission had to improvise.

3. Into orbit at last

NEAR entered orbit around Eros in February 2000. It became the first spacecraft to orbit an asteroid and was renamed NEAR Shoemaker in honour of planetary scientist Eugene Shoemaker. From nearby, an object previously seen as a distant moving point became a detailed landscape.

The dot in the telescope now had terrain.

4. A world with awkward geometry

Eros is elongated and irregular, so navigating around it differs from orbiting a neat spherical planet. Controllers adjusted the spacecraft's orbit to support mapping and other measurements. Instruments examined its shape, surface and composition, building a much richer picture of the small body.

Even orbiting a rock can require unusually careful bookkeeping.

5. Closer passes, sharper detail

During the orbital campaign, the mission made increasingly close observations. Images revealed craters, boulders and other surface features. Moving nearer improved resolution but also made accurate navigation more important. The mission was accumulating both scientific knowledge and practical experience around its unusual destination.

Every better photograph also meant less empty space underneath.

6. A different ending proposed

With the main orbital programme completed, the team considered a controlled descent. NEAR Shoemaker was not equipped as a conventional lander. Nevertheless, a gradual approach could provide close images and test whether the spacecraft might reach the surface gently enough to remain useful.

The final experiment asked the orbiter to become something it was not built to be.

7. Five burns toward the surface

On 12 February 2001, a sequence of manoeuvres slowed and lowered the spacecraft toward Eros. Images continued arriving during the descent. The surface filled the view in greater detail as distance disappeared, turning an extended orbital mission into a remarkably cautious encounter with the ground.

The last photographs were also a countdown in metres.

8. Contact without landing legs

NEAR Shoemaker touched down on Eros at a low speed and survived. Contact was made with parts of the spacecraft rather than a dedicated landing structure. The achievement made it the first spacecraft to land on an asteroid, adding a major milestone after its main task had already been completed.

An orbiter had arrived at the surface and refused to become wreckage immediately.

9. Still sending science

The spacecraft continued communicating from the asteroid, and the team collected additional measurements after touchdown. Surviving contact was therefore more than a brief engineering curiosity. The unplanned surface phase extended the mission's scientific return from a location no previous spacecraft had occupied.

The mission had reached its ending, then sent another message.

10. The missed appointment in perspective

NEAR Shoemaker's journey included a failed initial rendezvous, a successful return, a year of orbital study and a landing. Describing it as effortless would erase the interesting part. The final success depended on recovering from an earlier setback without pretending that setback had never happened.

The spacecraft that missed its first meeting ended up staying on the asteroid.