Designing and constructing a spacecraft to withstand these extremes is a tricky endeavor and requires considerable testing before launch. Benefiting from the lessons learned during the Mars Polar Lander and Mars Surveyor Program 2001 experience, as well as further reliability upgrades and subsystems used in previous successful space missions, the spacecraft is in a high state of development early in the mission's fabrication phase. Therefore, the mission engineering team is working on developing enhanced spacecraft reliability through extensive testing, (i.e., beyond normal integration and environment testing that occurs for most missions).