What happened to the Mars Climate Explorer in September

1999?

By

Leslie Palomino

Mars Climate Orbiter

Was the first of the two spacecrafts , that successfully launched on December 11, 1998 by

a Delta II 7425 launch vehicle. After 9 months long cruising, the craft arrived at Mars on

schedule, on September 23, 1999. After Mars Orbit Insertion (MOI), the spacecraft was

intended to become the first interplanetary weather satellite.

http://upload.wikimedia.org/wikipedia/commons/1/19/Mars_Climate_Orbiter_2.jpg

The Orbiter objectives

• monitor the daily weather• record changes on the Martian surface• determine temperature profiles of the

atmosphere • monitor the water vapor and dust content

of the atmosphere • look for evidence of past climate change.

So what happen on September 19,1999?

The Mars Climate Orbiter was intended to enter orbit at an altitude of 140.5–150 km

(460,000-500,000 ft.) above Mars. However, a navigation error caused the

spacecraft to reach as low as 57 km (190,000 ft.). The spacecraft was

destroyed by friction at this low altitude.

Why did this happen?

The navigation error arose because the contractors did not use SI units to express

their performance

What is SI?

is the modern form of the metric system and is generally a system of units of

measurement devised around seven base units. It is the world's most widely used

system of measurement, both in everyday and in science.

How was it built?

• The Mars Climate Orbiter was a box-shaped spacecraft about 2.1 m high, 1.6 m wide, and 2 m deep. The total spacecraft launch mass of 629 kg included 291 kg of propellant. An 11 square meter solar array wing, measuring 5.5 m tip-to-tip, and a 1.3 m high-gain dish antenna was attached by 2-axis pole.

http://upload.wikimedia.org/wikipedia/commons/4/42/Mars_Climate_Orbiter_during_tests.jpg

It could of been prevented • This was all caused by a human error in the software development,

back on Earth. The thrusters on the spacecraft, which were intended to control its rate of rotation, were controlled by a computer that underestimated the effect of the thrusters by a factor of 4.45. This is the ratio between a pound force and a Newton. The software was working in pounds force, while the spacecraft expected figures in Newtons; 1 pound force equals approximately 4.45 newtons.

• The software had been adapted from use on the earlier Mars

Climate Orbiter, and was NOT tested before launch. The

navigation data provided by this software was also NOT cross-checked while in flight. The Mars Climate Orbiter thus drifted off course during its voyage and entered a much lower orbit than planned, and was destroyed.

Project cost

• Total project cost was $327.6 million for both orbiter and lander. Out of this, $193.1 million were for spacecraft development, $91.7 million for launch, and $42.8 million for mission operations.