NASA - Jet Propulsion Laboratory

XLfit: Calculating the power curve of Curiosity

NASA’s Deep Space Network - managed by the Jet Propulsion Laboratory (JPL) - has 23 spacecraft and 10 instruments conducting active missions. All of these are important parts of NASA’s program of exploration of Earth, the solar system and the universe beyond.

This rover is bigger, better and hungrier

The new Mars Science Laboratory mission -- with its rover called Curiosity -- will land in August 2012. A primary mission objective is to determine whether Mars is or has ever been an environment able to support life. It will chemically analyze samples collected from soil or drilled from rocks, and it will also analyze rocks from a distance using a laser.

Curiosity will work on Mars for at least 687 Earth days. Its payload of science instruments is ten times the mass of its predecessors and carries double the number of instruments including cameras, an x-ray spectrometer, and radiation & UV detectors. All this takes power - lots of it. To make sure Curiosity could still power itself in all environments, NASA’s Jet Propulsion Laboratory was tasked with investigating how the rover’s generator and batteries will perform over time.

XLfit threw the dog a bone

They needed to produce tables of voltages as a function of battery temperature, current and state of charge. This needs to be known across an extreme range of variables. But you cannot test every combination for real unless thousands of experiments are done in an environment that mimics the Martian surface.

XLfit was used to fit curves and correct data for temperature disparities and to extrapolate the voltage table into regions that weren’t tested. For JPL engineers the problem is that the data isn’t always the cleanest or most complete. XLfit was used to fit data from hundreds of real experiments and build an appropriate model, which was then able to calculate the data needed to understand how to keep the rover powered up and ready at all times.

“We are pleased to have contributed to this really exciting project”, said Andy Vines, Product Manager of XLfit. “With over 70 built-in models and the ability to add your own, XLfit with Excel provides powerful analytics and real scientific value.”


Knowing how Curiosity’s power system will function in any one of hundreds of extreme environments is essential but without help can be a long - or practically impossible - process. For the rover mission it is not just a case of time saving, it would not have been able to do a complete analysis without XLfit.

XLfit helped make sure that Curiosity will not be running out of energy anytime before its 687 Earth day project, and will hopefully go on long afterwards. Improved accuracy of battery modelling increases confidence and reduces margin of error during operations. The mission is able to do more science without putting the rover in danger.

Other uses of XLfit at JPL

At JPL, XLfit is used on a regular basis for other analytical jobs such as solar cell performance curves.

XLfit has helped science make the most of Mars Science Laboratory. What could it do for you?


XLfit Desktop – showing fits & associated charts in the Excel WorkBook