A Lander that weighs as little as a sheet of paper

This is so cool.  The European Space Agency’s Rosetta space probe, which became the first man-made object to orbit a comet a few weeks ago, sent a lander down to the comet yesterday.  The comet is so small that its gravity is minimal – about 0.01% of Earth’s gravity.  So, the lander weighs about the same amount on the comet as a piece of paper weighs here on Earth.  This made landing on it very tricky, and staying on it even more tricky.  So, the engineers at ESA came up with a novel solution: put screws on the bottom of each let of the lander and have it screw itself into the rock of the comet when it landed!  As a friend of mine said, this lander did not land on the comet so much as it treated the comet as another spacecraft and docked with it.

Here is how NASA describes the landing:

Rosetta’s ‘Philae’ Makes Historic First Landing on a Comet
November 12, 2014
Image from Rosetta

After more than a decade traveling through space, a robotic lander built by the European Space Agency has made the first-ever soft landing of a spacecraft on a comet.

Mission controllers at ESA’s mission operations center in Darmstadt, Germany, received a signal confirming that the Philae lander had touched down on comet 67P/Churyumov-Gerasimenko on Wednesday, Nov. 12, just after 8 a.m. PST/11 a.m. EST.

A statement about Rosetta from John Grunsfeld, astronaut and associate administrator for NASA’s Science Mission Directorate, is online at:


The lander is expected to send images from its landing site, named Agilkia. These will be the first images ever taken from a comet’s surface. Philae will also drill into the surface to study the composition, and witness close up how a comet changes as its exposure to the sun varies. With its primary battery, Philae will remain active on the surface for about two-and-a-half days. Philae’s mothership, the Rosetta spacecraft, will remain in orbit around the comet through 2015. The orbiter will continue detailed studies as the comet approaches the sun and then moves away.

In addition to their well-deserved reputation as beautiful cosmic objects, comets hold vital clues about our solar system’s history. They are considered primitive building blocks of the solar system that are literally frozen in time. Comets may have played a part in “seeding” Earth with water and, possibly, the basic ingredients for life.

NASA provided three of the 16 instruments on board the Rosetta orbiter. The NASA instruments are: the Microwave Instrument for Rosetta Orbiter (MIRO); Alice, an ultraviolet spectrometer; and the Ion and Electron Sensor (IES), which is part of a suite of five instruments. For more information on the U.S. instruments aboard Rosetta, visit:


Rosetta is a European Space Agency mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; National Center of Space Studies of France (CNES), Paris; and the Italian Space Agency, Rome. NASA’s Jet Propulsion Laboratory in Pasadena, California, a division of the California Institute of Technology, Pasadena, manages the U.S. participation in the Rosetta mission for NASA’s Science Mission Directorate in Washington.

More information about Rosetta is available at:


DC Agle/Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov / guy.webster@jpl.nasa.gov


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3 responses to “A Lander that weighs as little as a sheet of paper”

  1. John Burnette says :

    How did they know the comet wasn’t spinning? That would have put a real crimp in their landing plans won’t it?

    • Graham Burnette says :

      I had assumed that it was spinning, since most things in space do have a rotation. Just makes the math harder in calculating the necessary trajectory, right?

      • John Burnette says :

        No, the trajectory calculation is the same, that is, deliver the craft to the general location of the comet, matching speed and direction – that part is the same if the comet is spinning or not. But if it IS spinning you have to approach it perpendicularly to the axis of rotation, while at the same time spinning the craft at the same rate. Keep in mind you get to do this with controls that have a built lag time measured in minutes.

        I’d love to hear how this was pulled off, especially if there was some way to measure the spin of the comet from a distance.

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