Goodbye EO-1

Last week I had to say goodbye to an old friend, a 17 year-old spacecraft called Earth Observing-1 (EO-1).

"EO-1 was a technology validation mission for testing cutting-edge advancements that have been and are being implemented on current and future satellite missions. The satellite launched in 2000 with 13 new technologies, including three new instruments, that had never been flown previously. Among its many accomplishments, the satellite was an innovator for detecting Earth’s biochemical constituents in unprecedented detail, a pathfinder for using artificial intelligence software for streamlined satellite communication and a precursor for extremely close flying between orbiting satellites."

For me, the EO-1 mission was the start of my career. I was fresh out of college with a B.S. in Aerospace Engineering and I had just landed a job with a very small company in Lanham, Maryland that provided engineering services for NASA at Goddard Space Flight Center. Within a few months of starting work I received my first major work assignment...ascent maneuver design work on the EO-1 mission. My main task on EO-1 was to figure out how to get the spacecraft from the orbit that the launch vehicle initially puts it in on launch day to the orbit it wants to be in operationally. EO-1 was a technology demonstrator mission and one of the technologies it was testing out was autonomous formation flying. If you have ever seen the Blue Angles or the Thunderbirds at an air show then you have seen formation flying...except this is with spacecraft. EO-1 was supposed to fly very close (about 1 minute behind) Landsat-7, a spacecraft that in 2000 was already in orbit above the Earth.

This image shows LandSat-7 in the lead with EO-1 imaging the same swath of the Earth 1-minute later

This image shows LandSat-7 in the lead with EO-1 imaging the same swath of the Earth 1-minute later

One minute may not seem all that close, but remember these are very expensive spacecraft and there isn't anyone sitting in the cockpit in orbit with them. Up until this point in time, if you wanted to move one of these spacecraft it would take days if not weeks of planning before the orbit maneuver was executed and the spacecraft was moved. With the technology we were demonstrating on EO-1 we were going to let the computer on-board EO-1 do all the maneuver calculations and execute the maneuver...all without anyone on the ground having to do anything. This was a first for NASA!

So my first task was to work with a very small team to come up with the sequence of maneuvers that would move EO-1 from the orbit it starts in after launch to a very tight formation flying orbit behind Landsat-7. Getting all of the orbit parameters just right to achieve the tight orbit we needed with Landsat-7 was no easy task and we needed to do it quickly and with as little propellant as know, so the spacecraft could continue to fly for 17 years! This work lead to my first professionally published paper.

The orbit ascent maneuver design wasn't my only task on EO-1. I helped out a bit with the on-orbit software the would perform the autonomous maneuver calculations as well, but my main task was leading the operation team that help operate the spacecraft from the ground (when the spacecraft wasn't testing out its autonomous capabilities). This involved writing a lot of scripts (computer code) that would generate products needed by other systems that supported the EO-1 spacecraft. Things like ground stations that would track EO-1 and help us communicate with the spacecraft. Ground stations needed to know where to point and for that they needed to know where EO-1 was in orbit above the Earth. So we had to generate specifically formatted files to tell the ground stations what they needed to know. I also had to write scripts to tell the spacecraft how to maneuver. It was one thing to figure out how long to turn on the spacecraft thrusters for, but then you had to tell the spacecraft in its own language how to do that. So we needed computer code to take a maneuver design (point the spacecraft here and burn for this long) and turn it into commands the spacecraft would understand.

So for several years leading up to the EO-1 launch in 2000 I worked on all of these things and then we launched. After launch I lead the team that used the maneuver strategy we designed to actually maneuver the spacecraft into its operational orbit. After EO-1 was safely behind Landsat-7 I also helped with the day to day orbit maintenance maneuver design and the efforts for testing out the autonomous algorithms on-board. After the autonomous maneuvers technology was successfully demonstrated I helped to train the operational team that would take over from there, doing the day to day things to support maneuver operations going forward.

EO-1 was an amazing start to my career. If you had told me as a kid that would be maneuvering a several hundred million dollar spacecraft right out of college I would have called you crazy. But I was in the right place at the right time I got to learn under some of most experienced and truly wonderful people I have ever had the privilege of working with. So EO-1 was more than just a spacecraft to me, it was the start of an amazing adventure that I am still on today. In fact, just last year as I was taking one of my last tests to get my Masters degree I had a question about the maneuver design for the EO-1 mission. I never in a million years thought I would be asked a test question about space that was based on my work.

EO-1 was "turned off" on March 30th 2017. This means the spacecraft was taken out of its operational orbit and put into an orbit that atmospheric drag will slowly and naturally cause to become lower and lower until in burns up in the atmosphere around 2056. So EO-1 may no longer be operational, but its kind of nice to think it will still be up there in orbit long after I retire. Thanks EO-1 and Godspeed...

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