365daysDate: June 18, 2009

Title: THEMIS/Artemis


Podcaster: CSE@SSL

Organization: Center for Science Education at UC Berkeley’s Space Sciences Laboratory

Description: THEMIS which stands for “Time History of Events and Macroscale Interactions during Substorms” is a constellation of 5 satellites and 30 ground-based observatories studying Earth’s magnetosphere and aurora. The main aim of these satellites was to answer fundamental questions concerning nature of an abrupt and explosive release of solar wind energy stored within the Earth’s magnetotail, known as a substorm. Having achieved most of its primary objectives of establishing when and where the substorms begin, the satellite mission will split up in July to become two missions. The first, THEMIS-Low, consisting of the three inner probes will continue to study the Earth’s space environment. The outer probes will explore the space environment of the Moon and renamed ARTEMIS: “Acceleration Reconnection Turbulence, and Electrodynamics of Moon Interaction with the Sun.” NASA has extended the THEMIS/ARTEMIS mission to the year 2012.

In this podcast we talk to Dr. Vassilis Angelopoulos, UC Berkeley, the PI of the mission, Dr. Manfred Bester, the THEMIS Mission Operations Manager and Dr. Laura Peticolas, the lead Education and Public Outreach scientist for this mission. We learn about the discoveries and insights learned from THEMIS, what we hope to learn from ARTEMIS and how these discoveries can be shared with the public.

Bio: Vassilis Angelopoulos, the principal investigator for THEMIS, is a Professor of Earth and Space Sciences and a member of the Institute of Geophysics and Space Physics at the University of California, Los Angeles. He also holds appointments at the Space Sciences Laboratory, University of California, Berkeley and at the NASA/Jet Propulsion Laboratory and has been the recipient of many awards including Macelwane Medal, conferred by the American Geophysical Union, Zeldovich Medal, conferred by the Russian Academy of Sciences, the Fullbright scholarship and Fred Scarf Award, conferred by AGU’s Space Physics and Aeronomy Section to the best Ph.D. thesis.

Dr. Manfred Bester joined Space Sciences Laboratory at the University of California at Berkeley in 1986 where he established the Mission and Science Operations Center and the Berkeley Ground Station. In his current position as Director of Operations he leads the Operations and Ground Systems group that has conducted on-orbit operations of eight NASA funded spacecraft – FAST, RHESSI, CHIPS and the five-spacecraft THEMIS constellation. As Mission Operations Manager he led the post-launch commissioning, navigation and science operations activities of THEMIS. At present, he oversees the planning and implementation of operations for the extended THEMIS mission that involves transfer of two of the five spacecraft from Earth to lunar orbits. In 1996 he founded Bester Tracking Systems, Inc. (BTS), a company providing software development and consulting services to the aerospace community. The flagship product of BTS is the SatTrack Suite. Manfred Bester has a doctorate in Physics from the University of Cologne, Germany. His areas of interest include mission analysis, multi-mission ground systems, process automation, space communications and operations, flight dynamics, software development and systems engineering. He is a member of AIAA, AGU, AAS, ASP and OSA, and a session organizer at the IEEE Aerospace Conference and at the SPIE Space Exploration Technologies Conference.

Dr. Laura Peticolas is an educator and scientist with many years of experience in studying the aurora and in teaching physics to undergraduates, teachers, and the public. She creates high school and junior college lessons, in collaboration with teachers and the E/PO team. She also organizes and teaches at professional development workshops. As the lead E/PO personnel of the FAST mission and an E/PO specialist working on the NASA mission, STEREO-IMPACT E/PO efforts, she leverages efforts from multiple NASA missions that are studying everything from the Sun to auroras.

Today’s sponsor: This episode of 365 Days of Astronomy is sponsored by the Physics Department at Eastern Illinois University: “Caring faculty guiding students through teaching and research” at


Priya: Greetings and welcome to the 365 Days of Astronomy podcast as part of the International Year of Astronomy. Today, we are going to get a chance to talk to Dr. Vassilis Angelopoulos, the principal investigator of NASA’s THEMIS mission. We also have with us here today Dr. Manfred Bester, the science and mission operations lead for THEMIS, and Dr. Laura Peticolas, the lead for THEMIS’s education and public outreach program. Welcome to you all.
Priya: THEMIS stands for Time History of Events in Macroscale Interactions during substorms. Now, that’s quite a mouthful, but in layman terms, what kind of things was THEMIS launched to study?

Vassilis: So, THEMIS was launched in order to determine which of the two competing theories that try to explain how explosions in space which take place in Earth’s environment— near Earth’s environment—are possible. Which of the two theories is correct regarding what causes those explosions. Those explosions in space are responsible for very sudden brightenings of the aurora borealis and australis and also for very abrupt acceleration of particles out in space that create huge currents that float down to the ionosphere that create, at times, havoc with power distribution grids. And also the same explosions accelerate electrons and ions to very high energies and cause particle radiation out in space and that particle radiation then causes damage to satellites in space and can really affect astronauts and can even be lethal at times. So we want to understand how those explosions are created, when do they get started, and how do they get started and we would like to be able to predict when they will take place so we can protect our satellites and we can avoid sending humans at those critical times having them outside the spacecraft so that we can protect them.

Priya: Oh, that’s really cool. But now, we’ve been reading that THEMIS has been a lot in the news lately. Can you describe some of the things about like space tornados that you’ve learned from the THEMIS data?

Vassilis: Sure. What has happened over the last two years is that THEMIS has been in its prime observation period and has been trying to address the primary question which is what causes these large explosions out in space, what causes and where is the energy that fuels those explosions, comes from, and what is the mechanism by which the particles get accelerated? So, the first question was answered back in 2008, when THEMIS made its first observations of this phenomena with five satellites lined up to track the flow of energy from one satellite to the other and to pinpoint the exact location of the particle acceleration. So, those observations were reported last summer and basically with those observations we can now claim that THEMIS has been a success in terms of achieving its primary objective. But, going beyond that, having five very capable satellites up in space one can do numerous things beyond its original scope of the mission was. And, so that’s what we have been doing over the last several months. We have used the satellites to try to understand space weather phenomena. Basically, how the flow of energy that starts from these explosions out in the environment, how does this flow of energy affect the near Earth space. And, what one of our teams has figured out is that once this energy comes rushing towards Earth it creates vortices out in space much like what you would have in atmospheric vortices when you have a tornado. And those we call “space tornadoes”. And much like in a vortex in the atmosphere where you have funnels and high speed atmospheric material, in a similar way, out in space you have funnels and high speed ionized gases that make it down to Earth, they touch ground, and in the process, because the space environment is charged, the motion of charges creates electricity, and those funnels, those vortices out in space are related with very large electrical currents. So, we have been able to measure those and link them from the ionosphere all the way out to space.

Priya: Now these explosions, do they pose a threat to humans?

Vassilis: Each individual explosion by itself creates a lot of energy but it gets diffused out in the vast regions of space such that this individual explosions in total do not carry enough energy. But, those when they happen in sequence, and when they are part of larger energy exchange between the Earth and the sun that we call magnetic storms, then they create enough radiation, enough acceleration of particles that they can cause significant problems/hazards to humans and to satellite systems. So, it is this potential for damage that lies within the little explosions that we are studying and because they are easier to study when they are isolated, we are lucky we are able to study them during solar minimum now and then carry this knowledge to the solar max that is coming.

Priya Dr. Bester we were just wondering, Dr. Angelopoulos said that you put up five space probes. Now, why five space probes? What’s gained by having five space probes?

Manfred: Well, the idea with THEMIS was to have five spacecraft that are equipped with identical sets of instruments, but then they would be strategically placed in orbit where we would bracket these regions of interest. We put three spacecraft in a one-day orbit, and another one in a two-day orbit and the fifth one in a four-day orbit. So they are all co-aligned, these orbits are co-aligned in space and then every four days they form this conjunction where they basically hover over certain regions in the sky for say twelve hours or so at the same time. And these orbits are aligned such and sized such that these regions where we assert these magnetic explosions occur are bracketed so you could tell by watching both the space and also the time sequences as to when something happens–which spacecraft sees it first and which sequence and what time delays. That way you can really come to these conclusions that we just discussed.

Priya: So, but now, two of the probes are to become the ARTEMIS mission, now is that correct?

Manfred: Yes.

Priya: Can you describe what the ARTEMIS mission is about?

Manfred: So, what we are planning to do is extend the THEMIS mission and there’s a dilemma that we are facing with the other two spacecraft in a sense that they will encounter rather long shadows that are happening next spring.

Priya: Shadows of?

Manfred: Shadows of the Earth. And they are so long, both the spacecraft will travel through some very long shadows of in the order of six to eight hours and we don’t have enough heating power, battery capacity to keep them warm during those shadows so it’s entirely possible that the remaining fuel will freeze and the batteries will discharge and we do not know if these spacecraft will come out of those long shadows alive. So, we have to do something to prevent that, obviously, we don’t want these two beautiful spacecraft just die and freeze. And we don’t have enough fuel to change the orbits either, but we do have enough fuel to evade in a different way. So a new mission phase was coined to basically send those two spacecraft on a new trajectory that leaves the Earth and put them eventually in a lunar orbit.

Priya: We have enough fuel to send them, to give them another push, to put them on the lunar orbit?

Manfred: Right, and surprisingly, we didn’t do that work ourselves, of course, but for this exciting mission extension we enlisted the help of the experts at the Jet Propulsion Lab who have determined, who designed the trajectories of interplanetary probes flying to Jupiter and Saturn, the Voyagers and the Mars missions and all of those, so they are the experts as to how you can take advantage of gravitational assists and steal a little bit of energy or change the orbits to or navigate through the solar system. So, they helped us with the mission design, to fly a trajectory, a so-called low energy trajectory which means you don’t go straight to the moon like the Apollo did, for instance or some of the other upcoming lunar missions. For those you need larger, very larger rocket engine and a lot of fuel to get straight away from the Earth and then also to go into lunar orbit instead of to expend more fuel to basically put the brakes on it, and wind up and otherwise you would overshoot.

Priya: So, what kind of science would the ARTEMIS mission hope to accomplish?

Vassilis: We’re going to study acceleration phenomena close to the moon’s orbit but, for the first time, with two satellites. After this two-satellite mission that will study what comes out of these explosions in near Earth space and propels itself to the interplanetary space. It will also study with the moon is on the side of the Earth towards the sun, it will study what comes out of the sun and how particle acceleration takes place in the solar, extended solar atmosphere which we call the solar wind. Now this is important to us because these accelerated particles, shocks that are coming towards Earth and its boundaries be wind slow and fast following speed and solar wind speed parcels. That particle acceleration is provides the seeds for galactic cosmic ray acceleration that is the number one risk for humans going to the moon and to Mars. So, human exploration depends on our understanding of how this particle acceleration happens in the heliosphere and being able to predict when the big events are coming–to avoid travel time during those periods and to be able to protect our astronauts that are going beyond the moon to other planets in the future.

Priya: Okay, now Laura, what kind of activities related to THEMIS has the Center for Science for Education here at Berkeley been involved in?

Laura: Well, at the very beginning of this program, the original well basically the idea was to put magnetometers which are instruments which measure Earth’s magnetic field or any magnetic field, but these are Earth based instruments to put these magnetometers in schools around the country and work with the teachers at those schools to teach them about the science of THEMIS, the science of the magnetic field of Earth and how space weather can affect Earth’s magnetic field, and have them be basically, partners in the THEMIS mission. And so that took place over the last four years and we have twelve magnetometers in schools around the northern United States, including Alaska and those magnetometers not only provide data to students, but they also provide the data, they are research grade magnetometers, so they also provide data for the entire science team. So, it’s been a really great collaboration because the teachers are able to feel like they are, and to be a part of, the THEMIS mission.

Priya: So, now if a school wanted to be involved in a future mission, like you know, in one of these upcoming missions in the next few years, cause 2012 is the year of the Solar Max and maybe it will be an exciting time to be a middle schooler or high schooler cause if you can see these, this stuff going on… Like if they wanted to be involved in the mission, how would they get in touch with you. I mean, do they get in touch with you or is there or how would they go…?

Laura: Well, there are a couple of different ways, probably, at this point, the best thing is to send anyone to our THEMIS website and that will then have a link to Heliophysics Educator Ambassador program which will have more resources kind of on a broader heliophysics theme. But if you go to the THEMIS website, that is:

Priya: Okay, that sounds really exciting. Well, good luck on the missions. Thank you very much. It was a pleasure talking to all three of you.

End of podcast:

365 Days of Astronomy
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