“We gave serious consideration to a number of add-ons, but in the end we accepted none of them,” says Jakosky. “The cost, the risk, the fact that it didn't benefit our mission—really, when you come in with a focused science mission for a Mars Scout-class mission, you have to do that. You have to pick and choose what you're going to do. One of the things that I'm proud of is that the original concept we proposed is what we're flying. We resisted science creep; we resisted engineering creep.”
Also contributing to the relatively painless development was a high degree of commonality with previous interplanetary spacecraft, including the Mars Reconnaissance Orbiter (MRO), the twin Stereo solar probes, the solar-powered Juno mission to Jupiter and the twin Grail lunar-gravity mappers.
“We really wanted to take, not only the heritage of the designs from previous programs, but we also really wanted to maximize the heritage of the people and the heritage of the tools that they used, the procedures,” says Guy Beutelschies, Maven program manager at mission prime contractor Lockheed Martin. “We really wanted to take all that and deliver a high-quality product while paying a lot of attention to the cost and the schedule.”
The basic structure of the Maven spacecraft follows the same design as the MRO, which is orbiting the planet now. Essentially, it is a hexagon of composite panels with the propellant tank in the center and the rest of the components and instruments hung on the outside or on an articulated payload platform that swings out from the main body. The hydrazine tank is larger than the MRO's to accommodate the particular needs of the mission, and the arrays and high-gain antenna are fixed instead of gimbaled for the same reasons.
Similarly, the instrument suite draws on heritage hardware to minimize development time and expense. “Nothing is being done from scratch,” says Jakosky. “Instrument development for the most part went smoothly.”
The principal investigator credits the planetary science managers at NASA headquarters for helping the Maven team stay on schedule and budget by keeping a steady and adequate stream of funding flowing. Also contributing was the tight planetary launch window, which focused mission development on simplicity as much as did the cost cap.
“The planetary launch period really drives a sense of urgency on the team,” says David F. Mitchell of Goddard Space Flight Center, the NASA project manager on Maven. “When you can launch any day of the year, every year, there can be a delay in making decisions sometimes. When we have approximately 20 days to launch, and then you stand down for 26 months, you're breaking the program. You're breaking it financially and, in the case of Bruce's science, you're breaking it because of the different timing with the solar cycle.”
Maven will arrive at Mars on Sept. 22, 2014, assuming launch at the beginning of the planetary window. A 39-min. burn of its main thruster, followed by five orbital adjustment maneuvers, should leave the 903-kg (1,990-lb.) spacecraft in a 6,200 X 150-km (3,850 X 93-mi.) science-mapping orbit inclined 75 deg. to Mars's equator.
At that point, the Sun will be just past solar maximum, giving the science team a chance to watch how the atmosphere reacts as the Sun's influence wanes. It will also be a good time in the 11-year solar cycle for major solar storms, so the spacecraft is well-equipped to measure their impacts on the atmosphere.