Like HowStuffWorks on Facebook!

How DIDO Works


DIDO in Space
An artist's rendering of the TRACE satellite, which learned new dance steps for its slewing procedure thanks to DIDO.
An artist's rendering of the TRACE satellite, which learned new dance steps for its slewing procedure thanks to DIDO.
Image courtesy of NASA

According to Elissar Global, the most extensive application of its software has been in space. This is probably the most intuitive application for DIDO being that vehicles and other machines in space rely heavily on automation or remote controls rather than direct human actions. Out there, a computer that can sense what's happening around it and quickly determine the best response is a valuable asset.

Two particular applications of DIDO have given software's reputation for solving optimal control problems quite a boost. The first of these was in 2006, when DIDO tackled the goal of maneuvering the International Space Station (ISS) 180 degrees within its orbital path without expending any fuel. Typically, the ISS and other vehicles in orbit must use thrusters to maneuver, which require expensive fuel. DIDO creator Ross and other researchers had an idea that a zero-propellant maneuver (ZPM) was possible.

DIDO was used twice for these zero-propellant maneuvers, each with success. On Nov. 5, 2006, the team maneuvered the ISS 90 degrees. Four months later, on March 3, they managed a 180-degree turn. These experiments were a large-scale proof of concept for DIDO, launching it into fame as the leading optimal control technology.

In 2010, another application of DIDO was to maneuver NASA's Transition Region and Coronal Explorer (TRACE) satellite. TRACE was on a mission to study the sun, but it had barely moved during its 12-year undertaking. As the TRACE research showed, NASA's protocol of following a straight line between two points may have identified the shortest distance to travel, but it was far from the fastest route. So, when the satellite needed to slew (move at an angle) to a new point, it was taking much longer than necessary, because it was trying to stick to that straight path.

The TRACE maneuvering research came just as the satellite was about to be decommissioned by the NASA Engineering and Safety Center (NESC). Engineers from NESC let Mark Karpenko take the lead in an experiment to apply DIDO calculations and uplink an optimal slew for the TRACE. The hypothesis was that the optimum path using gravity as an advantage would make for a more efficient approach to slewing. This idea relates to Bernoulli's principle in physics.

Despite its limited two-month turn around, the TRACE research team was able to prove its hypothesis. In addition, the TRACE required less than half the electrical power during each slew. Observers described the TRACE satellite maneuver as if it were dancing through space. Now that's what we call dancing with the stars!

Up next, we're dropping out of orbit and checking out how DIDO is making it big down here on Earth.