Instruments
Artist's Concept of InSight Lander on Mars: InSight was the first mission dedicated to investigating the deep interior of Mars. The findings will advance understanding of how all rocky planets, including Earth, formed and evolved.
Studying the Reflexes of Mars
InSight’s Rotation and Interior Structure Experiment, RISE, precisely tracked the location of the lander to determine just how much Mars' north pole wobbles as it orbits the Sun. These observations provide detailed information on the size, composition, and characteristics of Mars' iron-rich core.
Tech Specs
| Main Job | RISE tracked the wobble of Mars' north pole as the Sun pushes and pulls it in its orbit. This helps scientists determine the size and composition of Mars' core. |
| Location | Two Medium-Gain ‘horn’ Antennas (MGAs) on the lander deck, and an X-band radio transponder and transmitter in the lander's equipment bay, where electronics can be shielded from the harsh, cold conditions of space. |
| Mass | About 16 pounds (7.3 kilograms). |
| Antennas | 3 pounds (1.4 kilograms). |
| Transponder and Transmitter | 9.6 pounds (4.4 kilograms). |
| Power | 78 Watts (operated up to one hour per day). |
| Volume | 0.7 cubic feet (19.8 liters) total. |
| Electronics | 0.13 cubic feet (3.8 liters). |
| Medium Gain Antennas | 0.57 cubic feet (16 liters). |
"RISE helps us keep tabs on InSight! This tells us exactly where Mars is in space, and just how much the planet wobbles around in its orbit. This information will add to our knowledge of the size of Mars' core, and helps us determine whether it is liquid or solid."
5 Things to Know
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RISE Tracks InSightRISE tracks the location of the InSight lander every day and knows its location to within a few inches (centimeters).
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A Fast-Moving SirenRISE uses the same principle that causes the sound from a fast-moving siren to change as it moves away, to study Mars' core.
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Hard-Boiled or Raw?RISE helps determine whether Mars has a solid metal core, like a hard-boiled egg, or a molten, liquid metal core, like soft-centered, raw egg.
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RISE is Like a MirrorRISE simply sends back the signal sent to the lander from Earth, via the Deep Space Network, revealing the lander's location.
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Measuring Mars DaysAs the seasons change, carbon dioxide sublimates and condenses at the poles, causing tiny changes in the rotation rate of Mars, affecting the length of the Martian day. RISE will be able to measure these changes!
How It Worked
RISE worked like a mirror: it reflected a signal sent to the lander from Earth, and revealed the exact location of the InSight lander –and thereby, Mars – in space. In doing so, it measured changes in the frequency of the signal, known as the "Doppler shift.” Scientists can use this information, collected over the course of InSight's mission, to understand just how much Mars wobbles in its orbit. This is key to determining the size of Mars' core, and whether it is liquid or solid.
The Planets are Like Moving Sirens
As a siren approaches, it sounds higher in pitch than when it is moving away. This change in the sound is because of the “Doppler shift” in frequency due to the motion of the vehicle. If you know how the signal changes, you can determine how the vehicle is moving. Scientists can use this phenomenon to study the planets. They measure the difference in the original signal sent to RISE from Earth, and the signal that arrives at Earth from RISE. This information tells them how the lander is moving in space, and hence, how Mars wobbles in its orbit.
Tracking Mars' Wobble
We know that Earth wobbles every 18 years as it is pushed and pulled by the Moon. And with measurements from the Viking landers and from Mars Pathfinder, we know that Mars wobbles over one Mars year. But we don't yet know by how much. RISE helps scientists determine exactly how much Mars wobbles.
RISE Tells Us About Mars' Core
How much a planet wobbles depends on what's inside it. A hard-boiled egg spins faster than a raw egg. In the same way, a planet that is liquid at its core will wobble more as it spins than one that’s solid at its core. Understanding how much Mars wobbles will reveal what its core is like.
Scientists know that Mars only has a weak magnetic field frozen into the crust, but no field coming from its core today. What we learn about the core from RISE will help them understand why Mars' core isn’t generating a magnetic field like Earth's.