Modular Small Satellite Design for Responsive Tactical Applications

The requirement for small tactical satellites capable of satisfying a variety of missions on short notice has been studied as part of the AFSSD-sponsored RESERVES study. An innovative spacecraft design approach is described which makes use of pre-assembled subsystem modules. The design is successfully tested against the requirements of four example missions using three different launch vehicles, demonstrating ample design margins in each case. The approach holds promise of providing a simple, flexible cost-effective solution to the rapid-response requirements of the tactical military world

A Unique New Antenna Technology for Small (And Large) Satellites

The application of large antennas in spacecraft is often limited by available volume, as well as by the more usual mass limitation. Shroud dimensions usually determine the maximum aperture which can be carried without resorting to complex and potentially unreliable unfurling mechanisms. This applies all the more in a small-satellite environment with the smaller available launch volumes and severe mass limits of this species. FLAPS (Flat Parabolic Surface) is a newly developed technology for RF reflector surfaces which frees the spacecraft designer from the packaging rigidity of the common parabolic dish. It offers the ability to essentially duplicate the capability of a parabolic reflector in a reflector of almost any shape. The surface is shaped electrically rather than physically, in much the same manner as in a phased array, but by a totally passive array of dipoles suspended above a conductive ground plane. The dipoles are sized and spaced for the particular frequency and feed arrangement desired, and can produce a beam of essentially any desired shape. The FLAPS technology is applicable across the microwave and millimeter-wave spectrum. FLAPS reflectors have been built and tested at 2, 6, 16, 36, and 95 GHz. as well as at various other frequencies in this range. The technology lends itself to a variety of fabrication methods, which can be highly automated

A Low-Cost Small Satellite Space Radar System

The advantages of space-based radar have been frequently noted for such applications as environmental monitoring, crop detection, soil-moisture determination, coastal ice measurement, and all-weather surveillance, to name just a few. The FLAPSTM ( Flat Parabolic Surface ) antenna technology developed by Malibu Research, enables the conception of a smallsatellite radar system. The design described in this paper is that of a lightweight surveillance satellite capable of being launched on a Pegasus booster. It is capable of detecting small ships and aircraft, such as may be required for drug-interdiction missions and other all-weather surveillance applications. The FLAPSTM antenna has many of the features of a phased array antenna at a small fraction of the cost or mass ordinarily associated with phased arrays. Moreover, a FLAPSTM antenna can be folded or rolled and stowed in a variety of ways to enhance the possibility of fitting within the limited volume available in a small ELV. We describe approaches to packaging and deployment of such an antenna, and the mating of these assemblies to a Fairchild-developed small satellite, and to the Pegasus air-launched vehicle. The satellite features a fiber-optic data bus, and the integration of an on-board processor with a solid-state recorder as has been provided to NASA for its recently launched Small Explorer satellite

A Thermally-Integrated Spacecraft Design Approach Using Nuclear Dynamic Power Systems

The use of dynamic-cycle heat engines for space electric power systems makes it possible to design a spacecraft which is thermally integrated with the power system. The power system fluid loop is used to cool the spacecraft equipment and structure. This results in a spacecraft which is extremely insensitive to changes in sun-angle, eclipse periods, or power dissipation. Resultant temperature variations of equipment is seen to be a few degrees in the worst-case orbits, without the need for active thermal control. Organic Rankine and Brayton cycle generators are considered. Cycle power losses of less than one-percent are experienced in implementing this concept

Unique Features of Dynamic Isotope Power Systems for High-Requirements Spacecraft

The Dynamic Isotope Power System, designed for spacecraft requiring prime power in the 500-to-2000 watt range, has been successfully built and ground tested. A number of studies, summarized herein, have demonstrated the advantages of using such a power system instead of the conventional solar system, for a variety of earth-orbit missions. These advantages stem from the unique nature of the dynamic isotope system, different in kind from solar power systems. As a result, in many cases, the spacecraft design can be significantly simplified and more closely harmonized with mission requirements. This overall advantage can be crucial in missions which have stringent pointing, stability, viewing and/or positioning requirements

Extending the Useful Life of Radioisotope Thermoelectric Generators Through Active Power Control

The useful lift time of a Radioisotope Thermoelectric Generator (RTG) may be significantly extended by use of a "mobile-shunt" power conditioning system in preference to the more common shunt-dissipative type. A mobile-shunt regulator has been designed which automatically performs this function, as well as producing a regulated stepped-up DC voltage for the load

Nuclear Heat Sources for Cryogenic Refrigerator Applications

Spacecraft cryogenic refrigerators require thermal inputs on the order of 1000 W. First, the characteristics of solar-electric and radioisotope heat source systems for supplying this thermal input are compared. Then the design of a $sup 238$Pu heat source for this application is described, and equipment for shipping and handling the heat source is discussed. (LCL

Destabilization of dark states and optical spectroscopy in Zeeman-degenerate atomic systems

We present a general discussion of the techniques of destabilizing dark states in laser-driven atoms with either a magnetic field or modulated laser polarization. We show that the photon scattering rate is maximized at a particular evolution rate of the dark state. We also find that the atomic resonance curve is significantly broadened when the evolution rate is far from this optimum value. These results are illustrated with detailed examples of destabilizing dark states in some commonly-trapped ions and supported by insights derived from numerical calculations and simple theoretical models.Comment: 14 pages, 10 figure