Operation and performance of a second generation, solid state, star tracker, the ASC

The Advanced Stellar Compass (ASC) is a second generation star tracker, consisting of a CCD camera and its associated microcomputer. The ASC operates by matching the star images acquired by the camera with its internal star catalogs. An initial attitude acquisition (solving the lost in space problem) is performed, and successively, the attitude of the camera is calculated in celestial coordinates by averaging the position of a large number of star observations for each image. Key parameters of the ASC for the Ørsted satellite and Astrid II satellite versions are: mass as low as 900 g, power consumption as low as 5.5W, relative attitude angle errors less than 1.4 arcseconds in declination, and 13 arcseconds in roll, RMS, as measured at the Mauna Kea, HI observatories of the University of Hawaii in June 1996.     

ESA's Biopan 1--"Vitamin" experiment preliminary results

The purpose of “Vitamin” experiment is to study the efficiency of protective substances on three biological acellular systems aqueous solutions exposed to cosmic radiation in space. The first system “LDL”is a low density lipoprotein. The second is “E2-TeBG complexe” in which estradiol (E2) is bound to its plasmatic carrier protein, testosterone-estradiol binding globulin (TeBG). The third is “pBR 322”, a plasmid. “Vitamin” experiment was accomodated in the Biopan which had been mounted on the outer surface of a Foton retrievable satellite. The experiment was exposed to space environment during 15 days. A stable temperature of about 20 °C was maintained throughout the flight. “Vitamin” experiment preliminary results are presented and discussed.     

The data compression problem for the “GAIA” astrometric satellite of ESA

Space-based astrometry has a great tradition at ESA. The first space-based astrometric satellite in history, “Hipparcos”, was launched by ESA in 1989 and, in spite of orbital problems, was able to accomplish almost all of its tasks until it was finally shut down in 1993. The results of the Hipparcos mission were published by ESA in 1997 in the form of six CD-ROMs: the Hipparcos Catalogue contains 118,218 entries with median astrometric precision of around 1 milliarcsec, and specific results for double and multiple systems. In practice, Hipparcos drew for the first time the three-dimensional “map” of the spherical region of the Galaxy surrounding the Sun and having a radius of roughly 1,000 light years.

Then, in 1995, ESA launched the study of a new astrometric satellite, named “GAIA” and about a hundred times more powerful than Hipparcos, i.e. with median astrometric precision of around 10 microarcsec. This new satellite is intended to measure the parallaxes of over 50 million stars in the Galaxy, at least for the brightest stars, and this would mean to “draw” the three-dimensional map of the whole Galaxy, reaching out even to the Magellanic Clouds, 180,000 light years away.

The team of European scientists and engineers now designing GAIA, however, is facing hard technological difficulties. One of these is the design and coding of radically new and ultra-powerful mathematical algorithms for the on-board compression of the 50-million-stars data that GAIA will send to Earth from its intended geostationary orbit. Preliminary estimates of the raw data rates from the GAIA focal plane, in fact, are of the order of a few Gigabits per second. To reduce the data stream to the envisaged telemetry link of 1 Megabit per second, on-board data compression with a 1 to 1,000 ratio is the target. Clearly, this is far beyond the capabilities of any lossless compression technique (enabling compression ratios of 1 to some tens), and so some “wise” lossy compression mathematical procedure must be adopted.

In this paper a GAIA-adapted lossy data compression technique is presented, based on the Karhunen-Loève Transform (KLT). The essence of this method was already used by NASA for the Galileo mission when the large antenna got stuck and the mission was rescued by re-programming the on-board computer in terms of the KLT. That transform was officially named ICT — “Integer Cosine Transform” — by the NASA-JPL team led by Dr. Kahr-Ming Cheung. But the KLT here described for GAIA will of course differ from the JPL one in many regards, owing to the advances in computer technology.

Finally, estimates are also given about the possibility of using the KLT for onboard data compression in case GAIA is going to be put into orbit around the Lagrangian point L2 of the Earth-Sun system, and, above all, in case the number of stars to be observed is actually raised from 50 millions to one billion, as ESA currently appears to be likely to pursue.     

Dual-frequency ultrasound for detecting and sizing bubbles

ISS construction and Mars exploration require extensive extravehicular activity (EVA), exposing crewmembers to increased decompression sickness risk. Improved bubble detection technologies could help increase EVA efficiency and safety. Creare Inc. has developed a bubble detection and sizing instrument using dual-frequency ultrasound. The device emits “pump” and “image” signals at two frequencies. The low-frequency pump signal causes an appropriately-sized bubble to resonate. When the image frequency hits a resonating bubble, mixing signals are returned at the sum and difference of the two frequencies. To test the feasibility of transcutaneous intravascular detection, intravascular bubbles in anesthetized swine were produced using agitated saline and decompression stress. Ultrasonic transducers on the chest provided the two frequencies. Mixing signals were detected transthoracically in the right atrium using both methods. A histogram of estimated bubble sizes could be constructed. Bubbles can be detected and sized transthoracically in the right atrium using dual-frequency ultrasound.     

Countermeasure of the negative effects of weightlessness on physical systems in long-term space flights

The system of countermcasure of microgravity effects has been developed in Russia that allowed to perform safely long-term space flights. This system that includes different means and methods such as special regimens of physical exercises, axial loading (“Pingiun”) and antigravity suits, low body negative pressure device (LBNP, “Chibis”) and “cuffs” and others has been used with certain variations at certain stages of flight in 27 successfully accomplished space flights that lasted from 60 to 439 days. The pre-, in- and postflight studies performed in 57 crew members of these flights have shown that the system of countermeasure is effective in preventing or diminishing to a great extent almost all the negative effects of weightlessness in flights of a year and more duration and that the intensity and duration of changes recorded in different body systems after flights do not correlate significantly to flight durations, correlating strongly to the volume and intensity of physical exercises used during flight and especially during concluding stage of it.     

The pharao project: Towards a space clock using cold cs atoms

For several years, the “BNM-Laboratoire Primaire du Temps et des Fréquences” has worked on a cold atom frequency standard. With a cesium atomic fountain a resonance line width of 700 mHz has been obtained leading to a short-term stability of 2 × 10⁻¹³ τ^−1/2 down to 2 × 10⁻¹⁵ at 10⁴ s. A first evaluation of the fountain accuracy has been performed resulting in an accuracy of 3 × 10⁻¹⁵, three times better than previously achieved with thermal beams frequency standards. In the atomic fountain, gravity limits the interaction time to ˜1 s, hence the resonance line width to ˜0.5 Hz. A factor of 10 reduction in the line width could be obtained in a micro-gravity environment. The “Centre National d'Etudes Spatiales” (the French space agency), the “BNM-Laboratoire Primaire du Temps et des Fréquences”, the “Laboratoire de l'Horloge Atomique” and the “Laboratoire Kastler Brossel” have set up a collaboration to investigate a space frequency standard using cold atoms: the PHARAO project. A microgravity prototype has been constructed and operated first in the reduced gravity of aircraft parabolic flights in May 1997. It is designed as a transportable frequency standard. The PHARAO frequency standard could be a key element in future space missions in fundamental physics such as SORT (solar orbit relativity test), detection of gravitational waves, or for the realization of a global time scale and a new generation of positioning system.     

Economy of modular low-technology launch vehicles

The paper comprises an assessment of the design and the economics of so-called “low-cost” simple modular launch vehicles. It is shown that the performance is very marginal and that the cost per launch cannot compete with technically more advanced fully reusable vehicles. Especially a private-funded development cannot be amortized economically in case of an expendable launch vehicle.     

The hidden costs of reliability and failure in launch systems

In comparing the costs of different launch vehicles, the possibility of the risk of failure is assumed to be accounted for by the cost of insurance. The satellite may be insured against loss during launch, and the launch services provider may offer a “free relaunch.” However, actual costs of reliability and failure extend beyond this. Each failure necessitates an investigation and a “get well” programme by the operating agency, while putting the operations team “on hold” until services can resume. A commercial operator may also lose customer revenue and actual customers through loss of confidence or unavailability. Such costs tend to be hidden, and not evaluated in assessing the effectiveness of a system, but count towards total costs. Failure investigations help to improve system reliability, but this could equally have been achieved by expenditure in development and qualification. Reusable launch vehicles will have different costs associated with reliability and failure. The relationship between reliability and cost, properly assessed, ought to influence the design of both expendable and reusable launch systems.     

Innovations for competitiveness: European views on “better-faster-cheaper”

The paper elaborates on “ lessons learned” from two recent ESA workshops, one focussing on the role of Innovation in the competitiveness of the space sector and the second on technology and engineering aspects conducive to better, faster and cheaper space programmes. The paper focuses primarily on four major aspects, namely:

1. a) the adaptations of industrial and public organisations to the global market needs;

2. b) the understanding of the bottleneck factors limiting competitiveness;

3. c) the trends toward new system architectures and new engineering and production methods;

4. d) the understanding of the role of new technology in the future applications.

Under the pressure of market forces and the influence of many global and regional players, applications of space systems and technology are becoming more and more competitive. It is well recognised that without major effort for innovation in industrial practices, organisations, R&D, marketing and financial approaches the European space sector will stagnate and loose its competence as well as its competitiveness. It is also recognised that a programme run according to the “better, faster, cheaper” philosophy relies on much closer integration of system design, development and verification, and draws heavily on a robust and comprehensive programme of technology development, which must run in parallel and off-line with respect to flight programmes.

A company's innovation capabilities will determine its future competitive advantage (in time, cost, performance or value) and overall growth potential. Innovation must be a process that can be counted on to provide repetitive, sustainable, long-term performance improvements. As such, it needs not depend on great breakthroughs in technology and concepts (which are accidental and rare). Rather, it could be based on bold evolution through the establishment of know-how, application of best practices, process effectiveness and high standards, performance measurement, and attention to customers and professional marketing. Having a technological lead allows industry to gain a competitive advantage in performance, cost and opportunities. Instrumental to better competitiveness is an R&D effort based on the adaptation of high technology products, capable of capturing new users, increasing production, decreasing the cost and delivery time and integrating high level of intelligence, information and autonomy. New systems will have to take in to account from the start what types of technologies are being developed or are already available in other areas outside space, and design their system accordingly. The future challenge for “faster, better, cheaper” appears to concern primarily “cost-effective”, performant autonomous spacecraft, “cost-effective”, reliable launching means and intelligent data fusion technologies and robust software serving mass- market real time services, distributed via EHF bands and Internet.

In conclusion, it can be noticed that in the past few years new approaches have considerably enlarged the ways in which space missions can be implemented. They are supported by true innovations in mission concepts, system architecture, development and technologies, in particular for the development of initiatives based on multi-mission mini-satellites platforms for communication and Earth observation missions. There are also definite limits to cost cutting (such as lowering heads counts and increasing efficiency), and therefore the strategic perspective must be shifted from the present emphasis on cost-driven enhancement to revenue-driven improvements for growth. And since the product life-cycle is continuously shortening, competitiveness is linked very strongly with the capability to generate new technology products which enhance cost/benefit performance.     

Electrophotometrical studies of equatorial and tropical arcs on board the Salyut-6 orbital station

The results from the electrophotometric investigation of the equatorial and tropical ionospheric arcs on board the orbital station “Salyut-6”, carried out with Bulgarian photometer “Duga”, intended for measurements of the self-radiation of the Earth's upper atmosphere in the lines λ = 6300 Å, λ = 5577 Å, λ = 4278 Å and λ = 6563 Å, are analyzed. From the obtained results of the intensity of the measured emissions is established by calculation that the cause of these arcs is the plasma drift downwards, which leads to intensification of the dissociative recombination of the ions O₂⁺ and of the radiative recombination of O⁺.     

The earth explorer candidates: Nine focused missions, all satellite classes

The size of a satellite should follow naturally from the mission requirements taking into account implementation constraints, notably the choice of launcher and programmatics. The key concepts are “focused mission” and “maximum return for the investment”. The nine candidates proposed for the ESA Earth Explorer programme of research missions form a good representative set to illustrate a discussion of satellite classes. These focused missions lead to satellites from less than 100 kg and 100 W, to more than 2000 kg and 2 kW of power generation and include flights of opportunity and precursor experiments.     

Mars Direct: Humans to the red planet by 1999

“Mars Direct”, is an approach to the space Exploration Initiative that allows for the rapid initiation of manned Mars exploration, possibly as early as 1999. The approach does not require any on-orbit assembly or refueling or any support from the Space Station or other orbital infrastructure. Furthermore, the Mars Direct plan is not merely a “flags and footprints” one-shot expedition, but puts into place immediately an economical method of Earth-Mars transportation, real surface exploratory mobility, and significant base capabilities that can evolve into a mostly self-sufficient Mars settlement. This paper presents both the initial and evolutionary phases of the Mars Direct plan. In the initial phase, only chemical propulsion is used, sendig 4 persons on conjunction class Mars exploratory missions. Two heavy lift booster launches are required to support each mission. The first launch delivers an unfueled Earth Return Vehicle (ERV) to the martian surface, where it fills itself with methane/oxygen bipropellant manufactured primarily out of indigenous resources. After propellant production is completed, a second launch delivers the crew to the prepared site, where they conduct regional exploration for 1.5 years and then return directly to Earth in the ERV. In the second phase of Mars Direct, nuclear thermal propulsion is used to cut crew transit times in half, increase cargo delivery capacity, and to create the potential for true global mobility through the use of CO₂ propelled ballistic hopping vehicles (“NIMFs”). In this paper we present both phases of the Mars Direct plan, including mission architecture, vehicle designs, and exploratory strategy leading to the establishment of a 48 person permanent Mars base. Some speculative thoughts on the possibility of actually colonizing Mars are also presented.     

New results for the space radiation environment of MIR space station obtained by Liulin dosimeter-radiometer. Comparison with LET spectrometer NAUSICAA

Since 1988 high sensitivity semiconductor dosimeter-radiometer “Liulin” worked on board of MIR space station. Device measured the absorbed dose rate and the flux of penetrating particles. The analysis of the data hows the following new results:

In October 1989 and after March 24, 1991, two additional stable maximums in flux channel were observed in the southern-eastern part of South Atlantic Anomaly (SAA). These two maximums existed at least several months and seem to be due to trapped high energy electron and proton fluxes. In April 1991 additional maximums were localized in the following geographical coordinates regions: LATITUDE = (−35 °)–(−50 °) LONGITUDE = 332 ° − 16 ° and lat.(−46 °)–(−52 °) long. 360 ° − 60 °. Additional maximums diffusion occurs inside radiation belt. Appearance of these maximums seems to be closely connected with preceding powerful solar proton events and associated geomagnetic dynamics of new belt disturbances. After the series of solar proton events in June 1991 we observed significant enhancement of this new radiation belt formation. To achieve sufficient accuracy of dose rate predictions in low Earth orbits the structure and dynamics of new belt should be carefully analyzed to be included in a new environment model.

From the inter comparison of the data from “Liulin” and French developed tissue equivalent LET spectrometer NAUSICAA in the time period August–November 1992 we come to the following conclusions: Mainly there is good agreement between both data sets for absorbed dose in the region of SAA; Different situation of the instruments on the station can explain the cases when differences up to 2 times are observed; At high latitudes usually the tissue equivalent absorbed dose observations are 2 times larger than “Liulin” doses.     

Small spacecraft “UNISAT” launched by the “start-1” launcher

The preliminary estimations show that the contemporary level of electronic and information engineering makes it possible to create a small s/c of 150–200 kg mass capable to solve both the problems of Earth remote sensing and many other applied and scientific problems orbiting the planets at 500–1000 km. In accordance with the fundamental criterion for choosing parameters of small multipurpose spacecraft the small UNISAT s/c has been created on the basis of a unified space platform. The design provides for s/c energetic, thermal and space-saving parameters satisfying the conditions for accommodation of various-purpose payload and a possibility of using relatively inexpensive and light launchers like “Start-1” mobile launch complexes. Space platform mass is 100–120 kg; permissible payloads (PL) mass is 40–80 kg; maximal average power consumption of the payload is up to 60 W; three-axes orientation accuracy up to 0.001 deg./s; s/c lifetime is not less than 3–5 years.     

Lessons learned from Mir--a payload perspective

Among the principal objectives of the Phase 1 NASA/Mir program were for the United States to gain experience working with an international partner, to gain working experience in long-duration space flight, and to gain working experience in planning for and executing research on a long-duration space platform. The Phase 1 program was to provide the US early experience prior to the construction and operation of the International Space Station (Phase 2 and 3). While it can be argued that Mir and ISS are different platforms and that programmatically Phase 1 and ISS are organized differently, it is also clear that many aspects of operating a long-duration research program are platform independent. This can be demonstrated by a review of lessons learned from Skylab, a US space station program of the mid-1970s, many of which were again “learned” on Mir and are being “learned” on ISS. Among these are optimum crew training strategies, on-orbit crew operations, ground support, medical operations and crew psychological support, and safety certification processes.     

German rockets in africa: The explosive heritage of peenemunde

This historical paper reviews the technical development and the political impact of two “intelligence affairs” with German rocketry in African countries: 1. the Nasser missiles and space projects in Egypt during the 1960s; 2. the private OTRAG venture in Zaire and Libya during the 1970s.     

Stability and control of flexible satellites—II control

This is the second part of the investigation, the first part being “stability”. It is demonstrated that by monitoring the deformations of the flexible elements of a satellite, the effectiveness of the satellite control system can be increased considerably with the same given control system. A simple model of a flexible satellite was analyzed in the first part of this work. The same model is used here for digital computer simulations.     

PHYSIOLAB: a new laboratory for the study of the cardio-vascular system

On the basis of the experience gained during the previous french-russian missions on board MIR about the adaptation processes of the cardio-vascular system, a new laboratory has been designed. The objective of this “PHYSIOLAB” is to have a better understanding of the mechanisms underlying the changes in the cardio-vascular system, with a special emphasis on the phenomenon of cardio-vascular deconditioning after landing.

Beyond these scientific objectives, it is also intended to use PHYSIOLAB to help in the medical monitoring on-board MIR, during functional tests such as LBNP.

PHYSIOLAB will be set up in MIR by the French cosmonaut during the next french-russian CASSIOPEE mission in 1996. Its architecture is based on a central unit, which controls the experimental protocols, records the results and provides an interface for transmission to the ground via telemetry. Different specific modules are used for the acquisition of various physiological parameters.

This PHYSIOLAB under development for the CASSIOPEE mission should evolve towards a more ambitious laboratory, whose definition would take into account the results obtained with the first version of PHYSIOLAB. This “second generation” laboratory should be developed in the frame of wide international cooperation.