In January of 1992 representatives of the United States Air Force Academy (USAFA) met with the Center for AeroSpace Technology (CAST) at Weber State University to suggest a joint space exploration program. During the following months, several meetings were convened and plans solidified pursuant to begin project JAWSAT (Joint Academy Weber SATellite). The fundamental mission of project JAWSAT is to further the effective use of small, low cost satellites for aerospace education and to conduct valid scientific research in the use of non space rated instrumentation for low cost satellite design.
It is widely recognized that small satellites (smallsats) have inherent mission limitations, principally due to restrictions on mass, size, pointing accuracy, and available power. Consequently, to be successful, a supplier of remote sensing (RS) smallsats needs to have a thorough understanding of the end-users requirements. Furthermore, it is critical that users regularly interact with the smallsat technical team during all of the design activities. In concert with the supplier, the potential user must clearly define operational requirements such as revisit times, latency, mission duration, the quantity and quality of data, the sophistication of ground stations and the level of user control over the data processing and distribution. To further understand the requirements of Canadian and international RS data users, Spar Aerospace has conducted a number of studies in the last two years. These studies have specifically addressed the fields of ice monitoring, forestry, agriculture and land management.
After 30 years of in situ measurements of the Earth's magnetosphere, scientists have assembled an incomplete picture of its global composition and dynamics. Imaging the magnetosphere from space will enable scientists to better understand the global shape of the inner magnetosphere, its components and processes. The proposed inner magnetosphere imager (IMI) mission will obtain the first simultaneous images of the component regions of the inner magnetosphere and will enable scientists to relate these global images to internal and external influences as well as local observations. To obtain simultaneous images of component regions of the inner magnetosphere, measurements will comprise: (1) the ring current and inner plasma sheet using energetic neutral atoms, (2) the plasmasphere using extreme ultraviolet, (3) the electron and proton auroras using far ultraviolet (FUV) and x rays, and (4) the geocorona using FUV. An instrument complement of approximately seven imagers will fly in an elliptical Earth orbit with a seven Earth Radii (RE) altitude apogee and approximately 4,800-km altitude perigee. Several spacecraft concepts were examined for the mission. The first concept utilizes a spinning spacecraft with a despun platform. The second concept splits the instruments onto a spin-stabilized spacecraft and a complementary three-axis stabilized spacecraft. Launch options being assessed for the spacecraft range from a Delta II for the single and dual spacecraft concepts to dual Taurus launches for the two smaller spacecraft. This paper addresses the mission objectives, the spacecraft design considerations, the results of the MSFC concept definition study, and future mission plans.
Ball Aerospace has recently broadened its line of small satellites as part of the innovative and well-published DARPA `lightsat' initiative. This program, DARPASAT, has produced a small spacecraft bus that is highly capable, lightweight, and can provide significant services to the prospective payload. In addition, the bus is compatible with new small launch vehicles such as the Taurus and Pegasus. Of particular note, the bus-to- payload interface has been designed to maximize simplicity and modularity, all with the intention of easing the payload integration process and thus lowering the cost. As a result, the mechanical, thermal, and electrical interfaces are designed such that the payload can be integrated at the payload contractor's facility as a single entity, or `pallet.' This dramatically reduces the effort to then integrate this single pallet onto the spacecraft bus.
The CAMEO Program will integrate advanced optical and sensor technologies with the DARPA Advanced Technology Standard Satcl I I Ic lius (AISS 13) to (lelnonsirate and sIcc—qual i fy a new, I ight weight iuili ispeciral icniotc sensing small saicli itc. l'hc program offers an important iwo—fold opl)ortuIlity ( 1) to dcnonstratc technology that simultaneously addresses critical DoD and civil needs; and (2) to advance the concept of using small satellites for rapid, affordable capability insertion beyond DoD, into the civil/national space arena. The goals of the program are to: . Demonstrate "dual use", multi—purpose advanced ienioie sensing technologies for: (I ) l)ol) — Wide Area Surveillance; (2) Civil -Global Climate Research; and (3) Civil - Environmental Monitoring; S I)emonstrate the use of small satellites to rapidly augmilent on-orbit capability and affordably nrndernize both DoD and civil remote sensing satellite constellations; and . Deiiionstrate new payload operations concepts and the direct downlinking of usable data to DoD and civil consumers.
The Naval Center for Space Technology (NCST), the Navy's lead laboratory in space technology research and applications, was officially established in Washington, D.C. on October 1, 1986 as part of the Naval Research Laboratory (NRL). NRL has extensive facilities, experience, and a highly successful track record in space sciences and satellite systems development. As such, NRL is a national asset and source for spacecraft development, integration of space experiments, and testing of all ranges of space hardware. This paper provides an overview of the NRL space systems capabilities, beginning with a historical perspective and culminating with summary descriptions of the accomplishments and capabilities of each of the NRL space activities.
The advent of modern small satellites has ushered in a new era of space applications, utilizing relatively high-performance spacecraft for a variety of mission payload applications. Existing cost and risk analysis techniques developed over the last 30 years to support NASA and military space programs, however, are of limited utility for cost-effectiveness analyses of small-satellite programs. Understanding these limitations for high-performance small-satellite programs led NASA and DOD to seek better cost-analysis tools. This paper summarizes the Aerospace Corporation Small-Satellite Cost Model (SSCM) development process and presents an example of the cost analysis of a high-performance small satellite for remote-sensing applications.
TEG International I The Egan Group is a consulting firm which provides business, financial, market and policy services to organizations involved in space activities including communications, remote sensing, launch vehicles, and infrastructure.
We identified at least eight U.S. programmatic initiatives relating to the development and flight of small satellites, as well as about 50 individual small satellite missions being developed world wide for flight over the next five years. The proliferation of small satellites has led at least one U.S. congressman to introduce legislative language to limit their further development. There are many reasons for this intense interest in small satellites. One is simply the reaction to the increasing cost and development time for the larger space missions. The time scale alone is daunting. An individual scientist or engineer must almost be prepared to accept one or two major programs as a lifelong career, which becomes a significant disincentive for the more creative individuals. More significant is the fact that funding agencies are finding it increasingly difficult to gain support for the billion dollar plus missions that represent the high end of the space program.
ELOP, the largest electro-optics company in Israel, is developing the technological capability of designing an electro-optical space camera for earth resources monitoring. The capability being developed is a part of a major effort to lead large scale high-tech R&D programs for civil applications, such as astronomy, remote sensing, earth resources monitoring and navigation E/O sensors.
The NRL-801 (USA) experiment and other systems on the ARGOS (P91-1) satellite to be launched in 1995 can be used as a testbed for satellite navigational techniques, to explore unconventional means of measuring a satellite's position, velocity, acceleration, attitude and the local time. One way this is done is with measurements made using x-ray sensors. Parameters can be estimated onboard and verified through redundant determinations. The ARGOS satellite is being built under the Air Force Space Test Program. It carries eight experiments, three of which utilize far-ultraviolet (FUV) or extreme-ultraviolet (EUV) sensors and one of which (NRL-801) is an x-ray sensor. Among the ARGOS experiments NRL-801 uniquely has satellite navigation experiments as one of its prime objectives, with special design features supporting that purpose.
The Naval Research Laboratory (NRL) has been developing far- and extreme-ultraviolet spectrographs for remote sensing the Earth's upper atmosphere and ionosphere. The first of these sensors, called the Special Sensor Ultraviolet Limb Imager (SSULI), will be flying on the Air Force's Defense Meteorological Satellite Program (DMSP) block 5D3 satellites as an operational sensor in the 1997-2010 time frame. A second sensor, called the High-resolution Ionospheric and Thermospheric Spectrograph (HITS), will fly in late 1995 on the Air Force Space Test Program's Advanced Research and Global Observation Satellite (ARGOS, also known as P91-1) as part of NRL's High Resolution Airglow and Auroral spectroscopy (HIRAAS) experiment. Both of these instruments are compact and do not draw much power and would be good candidates for small satellite applications. The instruments and their capabilities are discussed. Possible uses of these instruments in small satellite applications are also presented.
An athermalized objective has been designed for a compact, lightweight push-broom camera which is under development at El-Op Ltd. for use in small remote-sensing satellites. The high performance objective has a fixed focus setting, but maintains focus passively over the full range of temperatures encountered in small satellites. The lens is an F/5.0, 320 mm focal length Tessar type, operating over the range 0.5 - 0.9 micrometers . It has a 16 degree(s) field of view and accommodates various state-of-the-art silicon detector arrays. The design and performance of the objective is described in this paper.
As part of its small satellite R&D activities, Spar Aerospace Limited is studying the applicability of onboard real-time data compression to solve some problems of data storage onboard small satellites and of data delivery to remote users. To fulfill this goal, a collaboration was established with the University of Surrey Spacecraft Engineering Unit to test Spar's compression code on UoSAT-5 EIS images and have it ultimately executed onboard UoSAT-5. Image compression of the UoSAT-5 remote sensing data has been achieved by a number of algorithms including lossy methods such as the `discrete cosine transform' (DCT) related to the JPEG standard, the `block truncation' (BT), the `vector quantization (VQ) as well as lossless compression methods.
The WEBERSAT microsat has been in a 500 km polar orbit of Earth since January of 1990. During this time an on board, low cost, color CCD camera has logged several dozen video images of Earth and heavens. Each new image has presented a unique challenge in restoration and image enhancement. Imaging from space is not a new story, in fact several space qualified sub-systems have proven to be highly reliable. The distinctiveness of the WEBERSAT imaging system is that it is not an expensive space qualified subsystem; rather, it is composed completely of slightly modified off-the-shelf commercial components as one would find from a consumer video store. Today's cost for such equipment is well under one thousand dollars.
The limited data rate of low-power small satellites often requires that images be data- compressed before transmission. Several data compression techniques are currently being developed and improved. These methods include: vector quantization (VQ), Lempel-Ziv, fractal encoding, and discrete-cosine transform (DCT) methods such as JPEG and MPEG. JPEG (Joint Photographic Experts Group) is a still-image compression system. MPEG (Motion Picture Experts Group) is a compression and communications protocol which defines a syntax for transmitting several data types, including audio, user-data, and full-motion compressed video. MPEG allows `tolerable' NTSC full-motion video transmission at data rates as low as 1.2 Mbps, and video-conference-quality transmission at rates as low as 56 Kbps. However, since the MPEG standard includes JPEG as a subset, it allows the transmission of compressed still images as well.
Every EOS satellite needs to down-link imagery (telemetry) and receive daily mission planning updates (commands). As image resolution has increased, down-link data rates and the required hardware to support the link functions have increased. A system design of a compact Integrated Command and Telemetry Subsystem is presented that deviates from this growth trend. The proposed system design is based on a modular packaging concept that offers high performance in a small (SEM-C) package. The design allows the modulation scheme, data compression approach, encryption, and image sensor interface to be tailored or changed by replacement modules. The design also features extensive use of built in test that helps to rapidly isolate anomalous operation both in test and on orbit. A discussion of how the method of modulation and data compression effects the efficiency of the link is presented.
The Miniature Sensor Technology Integration (MSTI) program sponsored by the Strategic Defence Initiative Office (SDIO) and executed by the Phillips Laboratory -- Edwards AFB is a satellite program specifically designed to demonstrate new SDIO sensor technologies. The MSTI spacecraft series performs experiments to characterize a wide variety of SDIO advanced sensor technologies in the low earth orbit (LEO) space environment. The technologies demonstrated on MSTI provide critical information for theater missile target and clutter background characterization. The launch of MSTI-1 on 21 November 1992 set a new standard in the development of small spacecraft and in the response time required to demonstrate space technologies.
The Spacecraft Fabrication and Test Manufacturing Operations Development and Integration Laboratory (SF&T MODIL) is working with SDIO program offices and contractors to reduce schedule and budget risks for SDIO systems as they go into production. The concurrent engineering thrust has identified potential high payoff areas. A materials and structures demonstration project has successfully completed a partial automated closing of matched metal molds for a continuous fiber composite. In addition to excellent accuracy, the parts demonstrated excellent predictability and repeatability of physical properties. The cryocooler thrust successfully demonstrated and inserted precision technologies into a generic cryocooler part. The precision technologies thrust outlined two potentially high payoff areas in precision alignment and miniature rocket thrust measurement. The Producible Technology Working Group (PTWG) efforts identified the need for a test and assembly thrust. Due to funding limitations, continuing efforts are limited to the cryocooler thrust.
Cryocoolers are essential components for many spacecraft. We summarize some spacecraft cryocooler requirements and discuss our observations regarding industry's current production capabilities of cryocoolers. The results of the Lawrence Livermore National Laboratory (LLNL) Spacecraft Fabrication and Test (SF&T) MODIL's Phase I producibility demonstration project is presented.
Multitask bus for small satellites is being developed at the University of Mexico (UNAM) for the conduction of LEO communications, remote sensing, and astronomical missions. The first prototype, SATEX-1, to be launched by Ariane in mid 1994, is a 50 Kg engineering test satellite with a primary communications payload and a CCD camera for low resolution imaging, as a secondary payload. SATEX-1 has been under design and development for several years and will be constructed by several research institutions, under finance from the Ministry of Communications (SCT/IMC). The structure is made of hybrid materials, including light aluminum alloys and composites. It has a three axis stabilization system. Attitude detection is realized by means of several sun and earth sensors. Electrical power is collected by two solar panels that are stowed for take-off, and deployed after separation. Thermal design is based mostly on passive components including radiators, shielding and orientation, but flat heaters are used in several places. Solid-state temperature sensors are used throughout the s/c to test and calibrate thermal models.
On September 1, 1993 Portugal had its first small satellite called PoSAT-1 launched on the Arianespace Ariane 4 launcher from Kourou, French Guiana, and placed into an 820 Km polar and sunsynchronous orbit. This launch culminates nearly 18 months work, including the projection of an experimental low cost star mapper in this satellite category. This paper describes an overall view of the system concept, where special efforts were dedicated in the use of commercially available components in compliance with typical constraints for small satellites.
It is becoming increasingly obvious that satellite bus technologies that have been developed for traditional larger satellite platforms are not always suitable for use with smallsats. This is due to the intrinsic smallsat limitations in size, weight, available power, and cost. 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 and Los Alamos National Laboratory are developing a system that determines three axis attitude through ultraviolet imaging of the earth's limb and adjacent stars. A nonconventional wide angle optics assembly and intensified CCD array are utilized for this purpose. Because of the stability and predictability 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 .02 degrees with a very small and lightweight sensor configuration. A prototype sensor has been fabricated and tested, and has met all performance objectives. A more advanced version is now being developed, and a flight prototype should be completed by the end of 1993.
The Phillips Laboratory Space Experiments Directorate in conjunction with the Air Force Space Test Program (AF STP), Defense Advanced Research and Projects Agency (DARPA) and Strategic Defense Initiative Organization (SDIO), are managing five small satellite program initiatives: Lightweight Exo-Atmospheric Projectile (LEAP) sponsored by SDIO, Miniature Sensor Technology Integration (MSTI) sponsored by SDIO, Technology for Autonomous Operational Survivability (TAOS) sponsored by Phillips Laboratory, TechSat sponsored by SDIO, and the Advanced Technology Standard Satellite Bus (ATSSB) sponsored by DARPA. Each of these spacecraft fulfills a unique set of program requirements. These program requirements range from a short-lived `one-of-a-kind' mission to the robust multi- mission role. Because of these diverging requirements, each program is driven to use a different design philosophy. But regardless of their design, there is the underlying fact that small satellites do not always equate to small missions. These spacecraft with their use of or ability to insert new technologies provide more capabilities and services for their respective payloads which allows the expansion of their mission role. These varying program efforts culminate in an ATSSB spacecraft bus approach that will support moderate size payloads, up to 500 pounds, in a large set of orbits while satisfying the `cheaper, faster, better' method of doing business. This technical paper provides an overview of each of the five spacecraft, focusing on the objectives, payoffs, technologies demonstrated, and program status.
This paper provides an update on the Space Technology Research Vehicle (STRV) project currently underway at the Farnborough site of the UK Defence Research Agency. The collaborative nature of the project is emphasized, and a description provided of the technologies to be demonstrated and the experiments to be conducted during the expected one year mission of the two small (approximately 50 kg) satellites in geostationary transfer orbit. The development status of the project as at March 1993 is indicated.