The Mars Climate Orbiter: How Important Doing the Right Calculations Is

The Mars Climate Orbiter was a NASA spacecraft launched in December 1998, embarked on a mission to study the Martian climate and atmosphere. This article explores the story of this probe, its objectives, the challenges it faced, and the lessons learned from its ultimately tragic end.

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Mission Objectives

This mission is part of the pair of probes of the Mars Surveyor program, together with the Mars Polar Lander, which was launched the following year in 1999. The primary goal of the program and this first part managed by the Mars Climate Orbiter was to collect crucial data on Mars’ atmosphere, weather patterns, quantity of water, and search proof of the climate variations over a long period. Equipped with a suite of scientific instruments, the spacecraft aimed to provide insights into the Red Planet’s atmospheric dynamics and seasonal changes.

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Scientific tasks

In collaboration with its colleague the Mars Polar Lander, the two probes would have given a 360-degree overview of what Martian weather is and was, from the ground and from the sky.

In particular, the entire meteorological system consisting of sandstorms, cloud and dust opacity, ozone, distribution and transport of dust and water was to be observed and studied daily by the new instrument called Pressure Modulated Infrared Radiometer (PMIRR).

Subsequently, the effects of topography on atmospheric circulation would be analyzed by the Mars Climate Orbiter Color Imager (MARCI), used for the acquisition of high-resolution data and images of the terrain.

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Launch and Journey

Launched in December 1998 on a Delta II rocket from Cape Canaveral, the Mars Climate Orbiter embarked on a journey of over nine months to reach Mars. During its cruise phase, the spacecraft conducted various scientific observations and calibration exercises in preparation for its orbital insertion around the red planet.

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A sudden disappearance

Tragically, the Mars Climate Orbiter’s mission ended abruptly on September 23, 1999, due to a critical navigation error. Everything seemed to be proceeding as planned and after waking up for the final approach maneuver, the coordinates for insertion into obits were sent, but something went wrong.

A signal sent to and from Mars takes around 10 minutes and 55 seconds to reach Earth due to the distance. The spacecraft passed behind Mars at 09:06 UT ERT (United Earth Received Time) and was scheduled to resurface and reestablish radio contact with Earth at 09:27 UT ERT, 10 minutes after engine ignition. However, contact was never reestablished, and no further signals were received from the spacecraft.

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Investigations begin

The unexpected loss of a $328 million spacecraft is a significant financial setback for everyone, so they immediately began the analysis to understand what had happened to the probe.

Despite the complexity of the space mission and the distance from Mars, expert scientists and engineers were able to determine the cause of the disaster within a few months. The spacecraft approached Mars at a lower altitude than planned, leading to a fatal atmospheric entry that resulted in the loss of communication, while the spacecraft itself crashed into the atmosphere.

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Why did that happen?

A navigation error was discovered during orbit insertion due to a lack of unit conversion between the US customary system (pound-force/seconds) and the International System of Units (newton/ seconds). The incorrect data caused the probe to pass by Mars at an altitude of 57 km instead of the planned 140-150 km; the denser atmosphere burned the probe due to friction.

This discrepancy was caused by the onboard thruster firing system, which interpreted commands as in the US customary system, while trajectory software assumed values were in the International System. Thus, orbital calculations were performed by assuming all thrusters had produced 4.45 times less impulse than in reality, leading to a position error.

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Lesson learned

Despite its unfortunate end, the Mars Climate Orbiter mission provided valuable lessons for future Mars missions. Despite numerous budget cuts at NASA, every future space mission includes several essential procedures. The real heritage of the Mars climate orbiter is the standardization of units of measurement. A single system of units of measurement is now used across all space projects. More rigorous and comprehensive testing of onboard systems was also implemented. Introduction of cross-checking systems also took place, with automatic mechanisms to verify data consistency.

Continuing Exploration

The legacy of the Mars Climate Orbiter lives on in the advancements made in Martian exploration. Its mission failure reinforced the importance of meticulous planning and communication in space missions, guiding future endeavors to explore and unravel the mysteries of the Martian atmosphere.

The Mars Climate Orbiter mission, though ruined by a navigation error, remains a testament to human ingenuity and the complexities of space exploration. Its story serves as a reminder of the challenges inherent in interplanetary missions and the enduring quest to unlock the secrets of our celestial neighbors.

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