THEMIS Looks at Phobos

These animations shows three views of the Martian moon Phobos as viewed by the Mars Odyssey orbiter. The apparent motion is due to movement by Odyssey’s camera, Thermal Emission Imaging System (THEMIS) rather than moon.

Each of the three panels is a series of images taken on different dates (from top to bottom): 29 September, 2017; 15 February, 2018; and 24 April, 2019. Deimos, Mars’ other moon, can also be seen in the second panel. These are visible light images, but THEMIS is mainly used for thermal-infrared scans.

Image Credit: NASA

THEMIS, Deimos, and Phobos

These images of Phobos and Deimos, the moons of Mars, were taken by the Mars Odyssey orbiter’s THEMIS (Thermal Emission Imaging System) camera using visible-wavelength light. The apparent motion of the moon caused by the camera’s point-of-aimaim being moved during the 17-second span of the observation.

The distance to Phobos from Odyssey during the observation was about 5,600 km. The Deimos was almost 20,000 km away.

Image Credit: NASA

Themis Sees a Magnetic Reconnection

This animation shows how the THEMIS mission observed auroral brightening resulting from a substorm in which solar particles and energy disturbed Earth’s magnetic field. The THEMIS orbits are shown in golden lines, and the Earth’s magnetic field lines are shown in blue. When solar material strikes the magnetosphere, the day side is pushed inward, while the back end magnetotail stretches out away from the Sun. When the stretched magnetotail finally snaps back, it starts to vibrate like a plucked guitar spring. As that happens, electrons in near-Earth space rapidly move toward the Earth’s poles along the magnetic field lines. As the electrons enter the upper layers of the atmosphere, they interact with oxygen and nitrogen atoms, releasing photons to create the aurora.

Video Credit: NASA


Some months ago, I presented a NASA video showing how two of the THEMIS satellites were repurposed for the ARTEMIS mission. This visualization shows a segment of ARTEMIS orbital paths. The satellite trails are are constructed in a lunar-centric inertial coordinate system so the trails reveal the motion of the satellites relative to the Lagrange points L1 and L2 (where the Earth’s and Moon’s gravity balance) in inertial space relative to the distant stars.

Video Credit: NASA

Building on the Work of THEMIS

The MMS mission will expand on the work of the previous THEMIS missions. The four satellites will fly in formation and be able to maintain their alignment with respect to each other by using GPS and sharing their location data with each other. Before I moved on to work on the ASTRO-H mission, I worked on the development of the prototype GPS receivers and other navigation radios for MMS.


Video Credit: NASA


A thin layer of cold, dense material called the plasmasphere surrounds Earth. Researchers using data from THEMIS have found that material in the plasmasphere can help prevent particles from the sun crossing into near Earth space.plasmasphereThe THEMIS mission observed how dense particles normally near Earth in a layer of the uppermost atmosphere called the plasmasphere can send a plume up through space to help protect against incoming solar particles during certain space weather events.Themis_plumeImage Credits: NASA



The Earth’s magnetic field which shields the planet from severe space weather often develops holes that allow the largest leaks of solar particles. This short animation shows what can happen based on findings from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission.

Video Credit: NASA


THEMIS (Time History of Events and Macroscale Interactions during Substorms)  is a mission to investigate what causes auroras in the Earth’s atmosphere. The program is run by NASA/Goddard Space Flight Center and not by the agency just up the road that forgot to buy both vowels.

I have never had any connection to the program.

UPDATE—I found this attempted comment while taking my morning coffee break.TK201404041329ZOf course, the IP address doesn’t belong to Amazon.IPlookup20140404Not only that, it’s not actively assigned.NoMatch

Hi, Neal!

UPDATE—Ooooo! Struck a nerve, have we? This comment just came in attributed to my late mother.TK2014041542ZCan you say “desperation”?