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“Mir Space Station” Website interview with
Former Flight Dynamics Officer (FDO) Roger Balettie

(note: this interview was originally done for the “Mir Space Station” website, which is no longer in operation)

How did you become a Flight Dynamics Officer (FDO) for NASA?

I graduated from The University of Texas at Austin with my Bachelor’s degree in Aerospace Engineering in December of 1985. I started work at the Johnson Space Center on January 6, 1986. Three weeks and two days before the STS-51L accident!!

I was originally hired to develop workstation software to support the Flight Dynamics Officers (FDOs) on the new Mission Control Center (MCC) workstations. After a short time of working with the FDOs, I knew that’s what I wanted to do. So, when the opportunity arose for a new FDO selection process, I submitted my application right away!

The selection committee conducted in depth interviews for all of the candidates and selected a small number of us from the large pool to start training for certification.

Can you describe some of the duties of the FDO?

The Flight Dynamics Officer (FDO, pronounced “fido”), in simplest terms, is responsible for “where the Shuttle is and where it is going”.

In more detail, the FDO is responsible for the overall trajectory, or flight path, of the Shuttle and all vehicles associated with it. To do this, a precise knowledge of the position and velocity of the Shuttle at any given time (also known as the state vector) must be known.

comonThe current definition of the state vector is accomplished by obtaining raw tracking data from either Earth-based RADAR sites or by using Doppler measurements from the Tracking and Data Relay Satellites. These raw data are then transformed into a best fit state vector by the Ground Navigation Flight Control position, a FDO support team member. The FDO then takes that vector and generates an ephemeris, or a prediction of where the Shuttle will be in the future. By using that ephemeris, the FDO can accurately determine what actions need to be taken to accomplish mission objectives, whether it is a ground-station fly-over, a rendezvous with Mir, or whatever.

The computation of trajectory events is a primary FDO responsibility as well. These events can include satellite deploy and rendezvous times, docking/undocking times, required trajectory corrections for payload customer needs, and many others. The ephemeris is also used for communications coverage predictions, attitude requirements, and a host of other needs.

The FDO is also responsible for the computation and execution of all translational maneuvers performed by the Shuttle. This includes everything from OMS-2 through the deorbit burn, all orbit raising or lowering burns, and all rendezvous or deploy/separation burns. The FDO will compute the required guidance targets, up-link them to the Orbiter, and make sure that the crew or the onboard computers have executed the burn correctly.

The FDO computes all deorbit and landing opportunities and is the primary point of contact with world-wide Shuttle landing sites. The FDO is the primary interface with the United States Space Command. USSPACECOM maintains a detailed catalog of all orbital debris and helps the FDO to ensure that there will be no collisions between the Shuttle and orbiting “space junk”.

What flights were you the FDO and of those which ones were you the lead?

I supported 26 flights as a FDO, including 10 as either a lead or co-lead FDO. My flight support also included (through my departure from NASA after STS-86), every Shuttle flight to Mir.

I was lead FDO on STS-51, STS-62, STS-70, STS-76, and STS-86. I was co-lead FDO on STS-43, STS-42, STS-54, STS-74, and STS-81.

What was one of the best times and one of the scariest times while you were the FDO?

The best times were always when we accomplished major mission objectives. It never mattered to me whether they were satellite deployments, major rendezvous burns, dockings with Mir. I was always thrilled to be a part of such a fantastic team doing such incredible things.

The “scariest times” were always in simulation conditions, thank goodness. The highly sadistic (but very talented!) training team at JSC made sure to throw the worst-case scenarios at us during our training prior to certification or flight. This way, any contingencies we saw during a mission were easy to solve and there was never any panic involved, because we had already seen *so* much worse during pre-flight training.

During shuttle missions to Mir, what extra steps do you have to do to perform your job?

I hope you don’t mind, but I’m going to answer that two different ways…

GroundUpFirst, anytime there is a Shuttle mission that is going to perform a “ground-up” rendezvous, there are additional steps performed by the FDO and the Flight Design community. A “ground-up” rendezvous means, simply, that there is already a target in orbit around the earth, and that we have to launch the Shuttle to rendezvous with it!

Those extra steps include tracking and state vector generation for the target vehicle, long-range computation of launch times on a variety of days, rendezvous plans, and rendezvous/docking times. These steps start at least a year ahead of time and continue, with increasing frequency, as we approach the launch day.

This differs from other types of missions (Spacelab or deploy/retrieve missions) where the launch time for any given day is usually dependent upon lighting considerations or other well-known times or events that don’t change as we approach the launch day. The launch time on a “ground-up” rendezvous is highly dependent upon exact knowledge of the target vehicle’s state vector. Launching at the wrong time could mean anything from a slightly degraded propellant margin to completely missing the mission objectives!

Second, Mir missions have a feel all their own when it comes to pre-flight preparation. The “awareness level” of the international implications really comes to bear. Mir missions had all of the “regular” amount of pre-flight prep as well as a entirely new set of requirements. There were several milestones prior to a Mir mission where a great deal of data exchange happened between us and the Russians.

What was it like working with the Russians? What are some of their strengths and weaknesses? What were some of NASA strengths and weaknesses?

From a Russian strength standpoint, their experience with prolonged manned spaceflight operations was apparent. Weaknesses have to be really addressed more as “cultural differences”. In particular, I discovered that they did not really care to have their computations or data questioned by NASA.

NASA strengths and weaknesses really were not that much different on Mir missions than on “standard” missions.

What are the major hurdles for constructing the International Space Station from the FDO stand point?

There really aren’t that many left now… the Phase I experience of working out all the pre-mission planning and real-time Flight Dynamics operations has been invaluable. I truly think that, from a trajectory standpoint, there aren’t many major hurdles left to overcome!

As I am not completely familiar with all the duties of an FDO, I welcome any answers to questions more relevant to your duties? Mir? and the International Space Station.

I think you hit them pretty well… good job!

Perhaps a few words about how the entire MCC, not just the FDO, was affected by the Mir missions. For instance, the MMACS (mechanical) Flight Control position now has to deal with the docking module, EECOM (environmental) has to include water and air transfer to Mir, PROP (propulsion) and GNC (guidance, navigation & control) have to be concerned with the Shuttle controlling the “stack” (combined Shuttle and Mir) attitude, FAO (flight activities) now schedules a great deal of transfer and joint crew operations, etc. In addition, there is a whole new Flight Control position, the Russian Integration Officer (RIO), whose entire function is to provide a single point of contact between MCC-Houston and MCC-Moscow!

Thanks Roger!

You betcha! My pleasure!!

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