Issue 125

This is the first of 3 articles I wish to share with you about the XSS-11 space experiment mission that occurred April 2005 to December 2006 in Low Earth Orbit (LEO). XSS means EXperimental Satellite System. It was an Air Force Research Laboratory (Kirtland AFB, where their Space Vehicles Directorate resides) developed mission to experience and experiment with rendezvous and proximity operations technologies and concepts in space using a small uncrewed/robotic spacecraft. It was the second in a series of XSS spaceflights planned by AFRL. In this first article, I will introduce the motivation for doing such a demanding, exciting, and eye-opening space experiment over a 1.5-year period. I will tell you about a short duration space experiment called XSS-10 that flew in 2003.It was a big step towards understanding micro-satellite RPO.

In preparing this XSS-11 review, I reflected to when I was the Space Vehicles Directorate’s Space Experiments Division Chief 2000-2001. I had a cadre of space technology dynamos who were driven to advance space technology and push to get promising space technology and concepts into space for experimentation. I want to introduce you to two of my mentors then. One of my dearest friend and mentor in the space business. His name – A. Clark Keith III, we called him Clark. He passed away May 2013 after a brave battle with cancer. I knew Clark since 1989 when I served my first assignment with then Phillips Lab. He was the “Gene Kranz” of the XSS-11, the Flight Director and much more including creator, innovator, and teacher. If you visit AFRL-Kirtland and go to the high bay of the big Aerospace Engineering Facility you will see in 2017 the high bay spacecraft area was named after him. A well-deserved honor. Another friend and mentor was Harold V. Baker, he went by Vern. Vern passed away March 2025. Vern was the XSS-11 Program Manager. He was determined and relentless. You needed a project leader like Vern to keep “daring greatly” (see Teddy Roosevelt’s “Dare Greatly” quote of 1910) and get hardware to space to shake it out and learn via experimentation. He was always kind to me. If I was off base on some topic or concept, he would share a grin or a “Vern scowl” and help me course correct, or engage in a fun-filled chat. I salute Clark Keith and Vern Baker and though there are many, many more amazing folks, I wanted to up front give them a shout out. Both took time before, during and after the flight of XSS-11 to share their thoughts as to where this RPO-thing might go. They were way ahead of the game! I thank them for being my friends and mentors.

Have you noticed via open press, there sure is a lot of rendezvous and proximity operations going on “out there,” Including some docking too. Hooray for all of it, I love RPO and docking (RPOD!) The Chinese and Russians sure are keeping the USA and her amazing astro smart Guardians (and others like out Intel folks) on the ball and attentive to their activity in LEO and GEO. In the past 5 years or so (maybe earlier), our adversaries really seemed to get rocking and rolling in the RPO on-orbit experiment operations. In my opinion, they are experimenting and then proving out operations concepts, I base this on open press articles by many experts and very competent writers. Well before this current hey-day in LEO RPO, in the late 1990’s, people like Clark and Vern and a fellow named Thom Davis, Program Manager for the first XSS mission called XSS-10, were championing space experiments to fly and test out RPO techniques using XSS small and very capable satellites. I saw their passion and dedication first hand.

RPO is not new to me. In 1982, I learned about RPO at Johnson Space Center, taught by a wonderful mentor named Chirold Epp. He showed the math, detailed the relative motion odd trajectories of RPO, and gave me an assortment of workbooks to study. I was hooked and educated by an amazing teacher. RPOD was on display in the Space Shuttle program with many RPOD missions to rescue pooped out satellites and missions to construct the ISS. The AFRL visionaries saw potential to do RPO for military purposes and tasks like spacecraft servicing and refueling. Clark and Vern and Thom were key visionaries, not the only ones. It was fun to watch and listen to Clark explain the concepts of RPO and kick in to teacher mode. They saw the military utility of a little spaceship with sensors, propulsion, cameras, and stuff like that maneuvering to fly-by something we were curious about or cozy up near it and fly formation to check things out (hey, that’s proximity ops). There was a lot of analysis and simulations, but we needed to “Just Do It.” They introduced to senior leaders and young ops center crewmembers the Clohessey-Wiltshire relative motion math, described RPO trajectories of a “chaser” in the vicinity of a “target” (relax, it is just terms for my discussion) and showed things like linear drift (think Ten One Rule!), natural motion circumnavigation, and forced motion station keeping. All using an XSS that would be designed, built, and flown with limited budget.

Long before the current RPO excitement we see playing out, the Air Force and folks like Clark, Vern and Thom and many others in the space lab arena (government and industry) saw the utility of RPO and set a course to go do space experiments and demonstrations. They and their fellow XSS-11 shipmates would overcome some challenges and would get to fly 2005-2006, but first there was an opening act in the RPO space experiment game. Read on, let us see what retired Lt Col Thom Davis had in mind!

In 2003, a short but very significant 1-day mission called XSS-10 hitched a ride on a Delta-II rocket lofting a GPS satellite. It jumped off once the GPS was clear and did a 24-hour RPO “dance” with the Delta II upper stage. XSS-10 was a small 65-pound spacecraft. The program manager was Thom Davis, a retired Air Force Lt Col. XSS-10 was to be the first in a series of XSS space experiment missions and was intended to demonstrate operational concepts and technologies relating to close-in satellite inspection operations. The XSS-10 was launched from Cape Canaveral on 29 January 2003. Eleven orbits later the XSS-10 ejected from the orbiting Delta second stage and successfully completed a series of semi-autonomous maneuver and inspection operations using the Delta second stage serving as a resident space object of interest. Operating autonomously, on a preplanned course, XSS-10 performed its mission of navigating around the Delta II second stage. Autonomously navigating around the second stage, at preplanned positions, the microsatellite took images of the second stage and sent them back in real time. Program Manager Thom Davis’s 18-page after mission report captures the history, team, design, on-orbit operations, and lessons of this “first out of the chute” XSS space experiment mission.

Here’s the link to his XSS-10 paper, it is a great read and sets the stage for XSS-11: https://repository.gatech.edu/server/api/core/bitstreams/86fe39c2-f1a6-429e-a900-ce238153aea7/content

I spoke with a young man who back then was an Orbital Analyst at the Kirtland AFB space operations center. He asked I leave his name out, but rest assured, he’s real and would go on to be a member of the XSS-11 team and further move onto many other exciting space missions advancing RPO concepts and more. ”I watched images streaming down from XSS-10 and thought this has amazing military utility and value.” His passion was noticed and he was selected to be a member of one of the earliest RPO teams. As part of that team, he was able to support the XSS-11 mission operations team, helping them grow experience in this exciting field.

We will end here and I will forecast what I will describe in the next XSS-11 article. Let us meet the team, a gathering of government and contractor partners who would build the XSS-11 and plan an exciting 1+ year RPO test mission on-orbit. We will learn more about the “little spaceship that could” XSS-11 spacecraft. A small but mighty ship with dedicated Air Force and contractor space folks at the helm as they put the spacecraft though it’s paces on-orbit. Long before the current RPO activity on display “out there,” a small team “dared greatly” to tackle RPO with their micro-satellite and experience the challenges of RPO and expand the depth of understanding of this capability. Until next time, let’s keep an eye on RPO happenings “out there.”