SPACES - An Integrated Software Approach for Attitude Determination, Control and Pointing Systems Analysis

The recent success of the Pegasus small satellite launch system by Orbital Sciences Corporation foreshadows radical changes to the satellite industry comparable to those which occurred in the computer industry when personal computers became commercially available alternatives to mainframes. In order to support low cost, fixed price contracts for small commercial satellites, engineering design cycles for satellites and satellite subsystems will have to be shortened, and accomplished with fewer staff to meet more stringent cost and schedule goals. To accomplish this, better design tools must be made available which will allow the mission analysis, requirements analysis, and other systems engineering tasks to be accomplished in an integrated software environment by a systems engineer. The Satellite Pointing and Attitude Control Engineering System (SPACES) is a software package developed as part of an integrated toolset by Honeywell Satellite Systems Operation to meet the need for altitude determination, control and navigation subsystems requirements analysis. SPACES is specifically designed to support initial mission analysis, pointing and tracking system requirements, as well as ACDNS sensor and actuator analyses. The approach used in SPACES was to take advantage of the state-of-the-art in user interface technology to provide a integrated system preliminary design tool that is easy to use with graphically oriented output that can handle a large class of satellite missions without requiring software modification

Ultraviolet Three Axis Attitude Sensor

It is becoming increasingly obvious that satellite bus technologies, which have been developed for traditional larger satellite platforms, are not always suitable for use with smallsats. This is due to the intrinsic limitations in size, weight, available power, and cost associated with the latter. The problem is particularly obvious for attitude reference sensors of both the earth and star viewing type. In response to the lack of suitable sensors for this purpose, Honeywell is developing a system that determines three axis attitude through ultraviolet imaging of the earth\u27s limb and adjacent stars. A non-conventional wide angle optics assembly and intensified CCD array are utilized for this purpose. Because of the intrinsic stability of the features being observed and the large number of pixels on which the scene is imaged, it should be possible to obtain accuracies on the order of .05 degrees with a very small and lightweight sensor configuration

Development of Honeywell\u27s Earth Reference Attitude Determination System (ERADS)

In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a very small low cost/power/weight attitude reference system designed for small satellite applications. We undertook this development because it appeared to us that small satellites require significantly smaller, lighter, and lower cost attitude reference systems than are currently available. ERADS was conceived as a single, strapdown, three axis sensor that would image the entire Earth\u27s limb in the ultraviolet. The spectral band was selected because it provided feature stability comparable to what is seen in the infrared along with sensor cost and weight characteristic of visible sensors. Although an Earth reference sensor was originally envisioned, it became evident that the ultraviolet was an excellent spectral band to observe stars as well, providing a providing a combined star/sun/Earth sensing capability in a single package. As a result, the current system can provide both three axis attitude and autonomous navigation data from a single solid-state sensor. A prototype sensor was fabricated in late 1992. In order to meet the weight and field of view requirements a highly innovative optical and detector assembly was developed. The optical assembly through the CCD has a volume smaller than a coke can and weighs less than a pound. The associated electronics, including an embedded R3000 processor, occupies two 8x10 inch boards. The system was originally designed to provide three axis accuracy of .05°. Subsequent evaluations indicated that a .02° accuracy can be obtained. In 1993 the optical system has been modified to be more compatible with typical satellite real estate priorities. The field of view has been extended to provide a clear 30° area in the center in addition to the original annular field. These modifications will make it easier to integrate ERADS with satellites and will also improve performance. The resulting sensor package now has a configuration more closely approximated by a tuna can. A processor design incorporating high density interconnect technology is being developed which will greatly reduce the weight and dimensions. The resulting package should fit within the tuna can envelope. As the system has evolved, it has become clear that better accuracy can be obtained by relying more heavily on stars for attitude determination, and using the earth limb data primarily for navigation purposes. The combination of earth and star sensing in a single small package should serve to further reduce the burdens of attitude determination for smallsats. The processor section of ERADS is scheduled for a flight test in 1994. The entire system is under consideration for an experiment on another 1994 flight

Electron Cloud at Low Emittance in CesrTA

The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. A range of EC mitigation methods have been deployed and tested and their effectiveness is discussed. Measurements of the electron cloud’s effect on the beam under a range of conditions are discussed along with the simulations being used to quantitatively understand these result