As promised earlier, I will discuss the Micro-Space SBIR (Small Business Innovative Research) proposals in this forum. I will discuss our C Proposal, “ Automatic Solar and Celestial Navigation on the Moon and Mars (O4.03-9181)” today. This has direct application to Lunar Rovers – particularly those rolling or hopping considerable distances – and even more application to human explorers. Only the simplest component is likely to be needed for GLXP (Google Lunar Rover) systems with their 500 meter travel, but that system is still very desirable.

It is easy to take for granted both the incredible performance of GPS and our classic road signs, which combine with good maps to make navigation fairly easy. Traveling where signs don't exist has always been “interesting”, without today's GPS data, and neither exists on the Moon or Mars. In theory, a GPS type cluster of satellites could be maintained around either body to provide GPS type data, but I am always talking about the first pioneers, not much later travelers, and these satellite clusters and their support systems are very expensive to install and operate.

Near term visitors to the Moon (or Mars) will find their navigational aids set back not just a century (with no GPS or road signs), but several millennia, since a “Magnetic Compass” is also useless: neither body, or any inner planet of the Solar system other than Earth, has a usable magnetic field . Fortunately, if the sun is “up”, it is usually visible on both bodies, so that “Celestial Navigation” has at least one good optical reference. Gyros, and particularly tiny, low cost MEMS units, have significant drift and can not provide a good directional reference for more than a few minutes. Even “Deductive Reckoning” needs a good directional reference to convert estimated motions into position changes.

Unless “Back Tracking” is totally reliable, a good directional reference must be maintained. Apollo operations on the Moon left highly visible tracks, but over rocky surfaces on Mars, tracks have not always been so visible. And, in a few hours, crisscrossing tracks can become dangerously confusing!

It would not be a good idea to operate even a short range, GLXP rover without a sustained directional reference so that planned travel can be closely approximated, and a clear line of sight to the lander need not be maintained. Small hills and dips, as well as radio “Surface Reflections” can severely degrade operations which depend on an uninterrupted link even over fairly smooth terrain, let alone the unexplored rough Lunar terrain which will be of most interest to follow on customers.

A simple Sun Sensor, with a few sensing elements and analog signal processing, can be sufficient for better than one degree absolute direction, provided that the travel history and clock time are known and the Sun Sensor can be kept level. A tilt sensor, optimally augmented by tiny MEMS gyros, allows a “Strap Down” system to work even better than one with moving gimbals and can work while the rover travels.

Six well matched and calibrated elements, for example, with good linearity, temperature compensation and low noise can cover the required 360 degree field of view with a fraction of a degree resolution. (This ignores the awkward “solar zenith” zone, with its +127 C lunar surface temperature at latitudes where it can occur.) Alternatively, 1000 low resolution “binary” light sensors can provide comparable resolution. The optical sensors must be able to monitor considerably more than the 2 Pi steradian upper hemisphere to accommodate low sun angles viewed by a tilted optical sensor.

The apparent sun direction is shifted by the tangent of the sun altitude angle times the roll angle perpendicular to the sun direction, for small offsets, with no first order effect from pitch errors along that axis. (The tangent factor of course “blows up” near zenith.) Both active and passive “levelers” can be used to remove these effects, but moving mechanisms are to be avoided whenever possible on a lunar craft and in any case have undesirable responses to motion transients. A “Strap Down” system, with no moving parts, is preferred and the computer data processing required is not a great burden.

Adding a tilt sensor (2 axis accelerometer), and tiny MEMS gyros, will produce both excellent short term directional information (from the gyro), and excellent long term direction – using averaged data from the optical sensors. These sensors mass less than a gram and eliminate all moving parts. Wheel motion data provides a linear velocity for the rover and is used for “Deductive Reckoning”. (Wheel slippage creates a navigational problem.) Acceleration offsets of the measured “plumb line” will be computed from this wheel motion data. Offsets due to the “centrifugal pseudo force” are computed as the cross product of the linear velocity and the vehicles angular rotation (radians per second) as it turns.

Determining the absolute position on the Moon (or Mars), to eliminate the errors that build up in “Ded Reckoning”, is more complicated, as is navigation at night or on the Lunar “Far Side”. Providing these with the same, trouble free optical package as the “Direction Reference”, taps more of the special expertise of Micro-Space, is the focus on our SBIR Proposal, and will be discussed in more detail another day.

NOTE: The SBIR program grants are officially, and very commonly in practice, “Dead Ended”. Although there is often an extension from Phase I “Feasibility Study” to Phase II, “Operational Breadboards”, the so called Phase III continuation – including production, for interested customers - must be funded through other private or agency channels. So called “SBIR Mills” specialize in completing the funded research , filing the required reports, and moving on to other topics with little expectation of a follow on. This is not the history of Micro-Space and its affiliates, which have delivered large quantities of “High Tech” products with little outside funding for research.

Developing NASA or Commercial customers for our proposed technologies will take some time, thus it is very important to start this process early, through a variety of marketing efforts: these discussions are one components of that effort. We welcome discussions with customers who could benefit from these technologies, and in every case could begin delivery of “Beta Test” hardware before the end of the SBIR projects.