Mars Climate Orbiter communication problem

The Mars Climate Orbiter (MCO) was a space probe launched by NASA to study the MArtian climate, atmosphere, ands surface changes. It was lauched on December 11 1998, but the communication with the spacecraft was lost on September 23 1999, when the spacecraft went into orbital intersetion.

The reason of this communication failure was becase a ground-base computer software produced an output in non-SI units, while a second systems that used those results expected them to be in metric units. The software that calculated the total impulse produced by the thruster firings during the Trajectory Correction Maneuver-4 calculated the results in pounds-seconds, instead of the spected output of newtons-seconds. The trajectory alculation used these results to correct the predicted position of the spacecraft for the effects of the thruster firings. This unit error made the spacecraft to encounter Mars on a trajectory that brough it too close to the planet, which cuased the spacecraft to desintegrate due to atmospheric stress when passing through Mars upper atmosphere.

This error was previously noticed by at least two navigator, whose concerns were dismised. The execution of Trajectory Correction Maneuver- 5 was then considered, which was also in the schedule, but it was ultimately not done.

Interview with Charles A. Abner

Charles A.Aber is the Shuttle Chief Engineer at  NASA's Kenedy Space Centre in Florida. We will proceed with the interview:

Interviewer:"When did you join NASA?"

Abner:"I joined NASA at the KSC in 1967 as an Apollo spacecraft ground system engineer. Then I joined the Air Force in 1968. In 1974 I rejoined the KSC and joined the lauch processing system team, where we build the space shuttle test and checkout hardware and software."

Interviewer: "What was your job back there?"

Abner: "I supervised the teams which where responsible for the development of ground launch software and also ground application software." 

Interviewer:"So, what is your job now in the Space Centre?"

Abner: "I'm responsible for all the engineering aspects which are related to processing flight hardware elements and facility/ground equipment, and also for the integration of technical decisions made by engineering and management personnel before and during launch."

Interviewer: "What kind of decisions do you make?"

Abner: "Well, I make engineering recomendations for final go/no-go lauch decisions. As the launch vehicle processing technical authority, I chair the Shuttle Engineering and Risk Review Boards."

Interviewer: "Last question: In how many missions have you participated since you joined NASA?"

Abner: "I've provided engineering integration to the space shuttle launch team for about 47 missions."

As you can see this was a short interview, but he didn't have time for more...

Well, I hope you like it. See you next time!!