The concept of this Voyager spatial vehicle artist includes his easily recognizable magnetometer boom. Credit: NASA/JPL-CALTECH
The audience is in love with the images returned to Earth by the space probes. Whether they show the moons of Jupiter, the rings of Saturn or the frozen surface of Pluto, these captivating images attract a lot of attention.
In addition to the cameras, the robotic probes always transport a series of scientific tools that obtain much less attention from the media, but these devices provide critical data that space scientists use to expand our knowledge on the solar system and the universe.
Among the most important tools are magnetometers. As their name suggests, they are devices that detect and measure magnetic fields. But how do magnetometers work and how are the information they collect useful?
Invisible forces around us
Many planets and moons and all stars generate magnetic fields. The Earth’s magnetic field, for example, is created by the melted and nickel iron movement in the nucleus of the planet and helps protect the earth from laden particles in the sun wind. If not controlled, these particles would destroy our atmosphere. The sun also generates a magnetic field due to the movement of the laden particles in the plasma of its interior. The magnetic field of Jupiter is so strong that it is second only to that of the sun in intensity.
The region around a body in which its magnetic field influences space is known as its magnetosphere. The magnetic field of Jupiter is so vast that its magnetosphere extends to the orbit of Saturn!
Because we study magnetic fields
The presence, strength and orientation of the magnetosphere of a body can tell scientists on a planet, the moon or the composition and the interior of stars (and often can be measured by a significant distance). The magnetic fields themselves cannot be filmed with normal cameras (although anyone who has played with magnets as a child can understand that they have defined forms and variable strengths). When humans began to send probes to space, they had to invent new tools to study invisible phenomena, including magnetic fields.
How magnetometers work
When designing a magnetometer, scientists must decide which aspect of a magnetic field want to study. Some magnetometers measure the strength of a magnetic field, while others detect its orientation. Still others can measure the rate of variation of strength and orientation over time. Robotic space probes can transport more than one type of magnetometer, with many subtypes of these existing devices.
Magnetometers can work in different ways. The simpler barn barrels that, if you pass through a magnetic field, generate an electric current. The voltage of that current provides information on the surrounding field. Other types of magnetometers calculate the way in which a magnetized material becomes or detecting the variation of the electrical resistance of an object after crossing a field. And some magnetometers use ionized (energized) gases to measure changes in the resistance and direction of the magnetic field.
The first spaces characterized some of these differences. The magnetometers transported by the Voyager 1 and 2 spatial vehicle consisted of two different devices: a high -field magnetometer (to measure very strong magnetic fields) and a low -field magnetometer (to measure weak magnetic fields). These devices measure the intensity of the magnetic field three mutually orthogonal axes at the same time and were used in different stages of the mission while the space vehicle approached, and therefore more distant from a particular target. Launched in 1977, at the time of the drafting of these magnetometers, they are still functioning and have provided large information on the magnetic fields of many moons and planets, as well as the space in addition to them.
Many other spatial vehicles, including most of the mariner probes, the pioneers 10 and 11, go, Europe Clipper, Cassini and Juno – to name just a few – have transported one or more magnetometers to the depths of the space.
Capture
The space probes are, in general, made with metals with many electronic parts. As such, the craftsmanship itself generates a magnetic field. It is essential that any magnetometer positioned on a space vehicle is not influenced by the space vehicle itself. What this means in practical terms is that, with a rare exception, the magnetometer must be positioned as far from the core of the possible space vehicle.
Many space probes make use of long and rigid structures called boom to maintain the magnetometer as much as possible from the main spatial bus (or body). These booms are in the foreground on Pioneer 10 and 11, Voyager 1 and 2, Cassini and other space vehicles. While primary magnetometers are often placed on the tip of a boom, scientists often position a second or even a third magnetometer in different points along the boom so that the magnetic fields generated by the space vehicle itself can be measured and subsequently taken into consideration by the measurements.
The magnetometer boom can be very long. The booms on travelers are almost 43 feet (13 meters) and 23 centimeters long) and the boom on Cassini extends for 36 feet (11 m) of length. While space vehicles that require only short boom can use rigid rods for their magnetometric booms, the longer booms tend to be elaborated lacticelike structures that can be compressed in small containers to adapt to the aforementioned winding of a rocket nose cone. Once free from their launch vehicles, these booms are extended to their entire length and become rigid (therefore they cannot be withdrawn).
More than the cameras
The cameras aboard the space probes are of fundamental importance, as they can show our eyes the wonders of the cosmos. But while the scientific tools, including magnetometers, are much less glamorous and attract much less attention, these tools are improving our knowledge and understanding of the space in countless ways and are often the unjected heroes of space missions.
