This graph illustrates that models used to predict the atmospheric entry details of the Mars Exploration Rover Spirit were right on track. The red curve shows the estimated change in temperature as Spirit descended through the martian atmosphere, from 80 kilometers (50 miles) to the altitude just above parachute deployment. The estimated profile was reconstructed from accelerometer and gyro readings taken by the spacecraft during its descent. This data roughly matches that of the blue curve, which represents the temperature profile predicted before landing. The predicted profile was generated from observations made at Gusev Crater on December 27, 2003, by Mars Global Surveyor Thermal Emission Spectrometer.