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Online From Jupiter 97

Greg Harrison

Technical Group Leader, Galileo AACS and Power Operations

a photo of Greg Harrison

My Field Journals

My name is Greg Harrison, and I'm a member of the Galileo Attitude Control and Power Operations Group. We support the Galileo Orbiter Engineering Team (OET) and the Galileo Science and Sequence Office (SSO). There are approximately 30 people in my group. My work involves the spacecraft's dynamics and control, pointing, and articulation of the scan platform (where the remote sensing instruments, or cameras, reside). Technically, I have been most closely supporting our Uplink team. The Uplink Team is the portion of the Group (about 8 of us) who actually design spacecraft activities at the command level and work with the OET and SSO to make these commands part of a sequence.

Much of my work has been related to Stars and Bright Body analysis. The "Stars" work refers to identification and validation of "Star Sets". Star sets are simply sets of 2 to 4 stars which the star scanner identifies in order for the spacecraft to figure out where it is pointing. I am one of the people that searches for potential star sets that will work without ambiguity. "Bright Body" work refers to analysis which determines when planets or moons can wreak havoc on the star scanner: either via actual damage due to extreme brightness, or by confusing the star scanner algorithms by looking "star-like".

In both cases, we want to prevent these things from happening. So, I run a ground software program called GSBI (General Solar Body Information) which gives me tons of data on the solar system's bodies and planetary moons. Then I analyze this data to ensure that we know when bodies (such as the Jovian moons) cause problems. When needed, I make inputs for spacecraft commands which will prevent the bright bodies from interfering with our stars, and from damaging the star scanner. Since I'm a Group Leader, I also handle and support some management and personnel work as well.

I have been at JPL since January of 1992. Before that, I was a Captain in the Air Force, supporting Space related technology demonstration work at the Pentagon and Los Angeles Air Force Base. This work was mostly in support of the Strategic Defense Initiative (also known as "Star Wars"). During this time I focused on "Interceptor technologies" - rocket propulsion, miniaturized guidance and control hardware and lightweight structures - all needed to meet the ambitious cost and performance goals.

As far as my career goes, I am not following some well-conceived, planned out itinerary. Looking back, it might seem that way. But really, each step was made by small decisions. Along the way, starting as far back as high school, I made choices, these choices are as simple as " would I rather take college prep classes in high school, or business related classes?".

When I graduated from high school I decided to pursue "engineering and science". That is about as specific as I was thinking. So, I decided to go to MIT rather than other colleges because they offered a great deal in areas that I was interested in. I also realized that MIT is on the expensive side - so I applied for an ROTC scholarship (Reserve Officer Training Corps). This full scholarship paid all my tuition in exchange for being an officer in the Air Force for at least 4 years. Seemed like a good deal. Of course, the Air Force wanted me to major in Electrical Engineering, but I was more interested in Aero-Astro and Mechanical Engineering, and Earth and Planetary Science. I decided to petition to set my major as Aero -Astro, which was accepted by the Air Force. I graduated in 1986, became a Lieutenant in the Air Force. Worked in the Air Force space program for 5 years, and decided to leave the Air Force and work in the civilian space world.

There are many "best things" about my job: Number one is probably the fascinating nature of the job and the people who do it. I love the romantic side of this job - in a very real sense, we are all explorers and Galileo is our telescope. I also am very happy that I can be a part of such a great team - a team with many amazing people on it. And I love telling people what I work on - explaining it to them in a way that it is tangible and exciting.

As far as things that I like least about my job, I would have to say it is frustrating when issues get decided for other than technical reasons, although I understand that there are times when it is important. Also, it is sometimes difficult being a team leader because people criticize your decisions. I've learned that you can't please everyone, and chances are, someone will be unhappy about a decision. I'm beginning to get more accustomed to that though.

Preparation for this job

All my life, I've been curious as to why things work, and what things are made of. Also, I've always been in awe of amazing feats such as the launching of a rocket, or the Apollo landing on the moon. And I've always been interested in man's search for how we fit into the universe. As a kid (and now too) , I liked to look at the moon and the stars. I used to think about why some people think the Earth is flat, and why others don't. I remember seeing a shooting star, and thought it was fascinating. So I guess one important thing is that I just like this stuff! Another key thing was that I had a decent flair for solving math and chemistry and physics problems, and that I enjoyed being able to figure them out.

My advice to students who would like to work in the field of Space Exploration, is two fold: Go outside and look at the stars and the planets. If you're like me and many people that work at JPL, you are interested in the Earth and the stars and how they all came together. I think that zest is important. The other part is study your algebra, your trig, your calculus, your chemistry, your physics... but don't forget your literature, your English, your foreign languages... Just enjoy learning - because once you start enjoying it, it never stops.


My dad is an electrical engineer - and he probably had a fair amount of influence in terms of following a technical career. I met interesting and brilliant people in college who inspired me to be curious and to explore. One of my college professors, Dr James McCune, convinced me to stick with Aeronautics and Astronautics, even though I wasn't so sure of myself. I am grateful to him for that advice.

Personal info

I just turned 31 years old. I am recently engaged to be married next year. I live in Altadena California. I grow delicious tomatoes, zuccini and eggplant in my garden. If you ate one of my tomatoes, you would't be satisfied with a store-bought tomato ever again! I enjoy comedy and I perform improvisational comedy regularly with my group, the Legitimate Freaks. We are funny - really! I am currently studying Improvisational acting and comedy at the Groundlings in Hollywood, and at Upfront Comedy in Santa Monica California. I'm a big Red Sox fan, and I'm hoping they go all the way this year, but if not, at least finish way ahead of the Yankees.



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