Small satellite's role in future hyperspectral Earth observation missions

Along with various advanced satellite onboard sensors, an important place in the near future will belong to hyperspectral instruments, considered as suitable for different scientific, commercial and military missions. As was demonstrated over the last decade, hyperspectral Earth observations can be provided by small satellites at considerably lower costs and shorter timescales, even though with some limitations on resolution, spectral response, and data rate. In this work the requirements on small satellites with imaging hyperspectral sensors are studied. Physical and technological limitations of hyperspectral imagers are considered. A mathematical model of a small satellite with a hyperspectral imaging spectrometer system is developed. The ability of the small satellites of different subclasses (micro- and mini-) to obtain hyperspectral images with a given resolution and quality is examined. As a result of the feasibility analysis, the constraints on the main technical parameters of hyperspectral instruments suitable for application onboard the small satellites are outlined. Comparison of the data for designed and planned instruments with simulation results validates the presented approach to the estimation of the small satellite size limitations. Presented analysis was carried out for sensors with conventional filled aperture optics.     

Lunar base development missions

On 20 July 1969, humankind first set foot on our Moon. Since then we have developed the Space Shuttle, explored most of the planets, cooperated in the development of the International Space Station, and expanded our knowledge of the universe through use of systems such as the Hubble Space Telescope and the Mars Pathfinder. After just five human follow-on missions to our Moon, we have returned robotically only twice to orbit, to map the surface and explore for resources.

The indication of the presence of hydrogen concentration at the poles of our Moon found by Lunar Prospector has added a new perspective for groups studying and implementing future lunar missions. Plans for nearterm missions such as the European Space Agency (ESA) “Euromoon 2000”, the Japanese Lunar A and Selene, and the Mitsubishi ”Earthrise 2001” Project, along with follow-on phases to the Lunar Prospector, are the beginning of humankind's return to the Moon. Organizations such as the International Academy of Astronautics have long championed the “Case for an International Lunar Base,” and a vision of a commercially-based lunar program has been outlined by several groups. A Lunar Economic Development Authority (LEDA) promoted by the United Society in Space was promulgated by the filing of articles of incorporation in the state of Colorado on 4 August 1997. This non-profit corporation has as its goal the orderly development of the Moon, through issuance of bonds to international private citizens and business entities who care to invest in its long-term development.

This paper draws from the works of the aforementioned, and specifically from the International Academy of Astronautics Lunar Base Committee, to structure a series of architectures leading toward eventual international commercial colonization of the lunar surface. While the prospect of fully reusable transportation systems utilizing fully developed lunar resources to perpetuate the permanent lunar infrastructure is enticing, this is a goal. We must utilize our current and near-term capabilities to re-initiate human lunar presence, and then build on emerging technologies to strengthen our capabilities. Humankind's return to the Moon is a part of our destiny. We can return in the near future, and then proceed to a commercial, permanent settlement in the 21st century.     

Manned missions to Mars: Minimizing risks of failure

Some major risks-of-failure issues for the future manned missions to Mars are discussed, with an objective to address criteria for making such missions possible, successful, safe and cost-effective. The following astronautical and instrumentation-and-equipment-reliability related aspects of the missions are considered: redundancies and backup strategies; costs; assessed probability of failure as a suitable reliability criterion for the instrumentation (equipment); probabilistic assessment of the likelihood of the mission success and safety. It is concluded that parametric risk modeling is a must for a risk-driven decision-making process.     

Medical concerns for exploration-class missions

The Space Exploration Initiative will challenge life scientists with a diverse set of crew medical risks. The varied sources of this cumulative risk are identified and briefly discussed in terms of risk assessment and preliminary plans for risk management. The roles of Space Station Freedom and other flight programs are discussed in the context of exploration medical objectives; and the significant differences between Space Station era (second generation) and exploration medical support systems (third generation) are reviewed.     

Dosimetric measurements in manned missions

Detector packages consisting of thermoluminescence detectors (TLDs), nuclear emulsions and plastic nuclear track detectors were exposed in different sections of the MIR space station, inside the Spacelab during the IML1 mission, and inside Spacelab module and tunnel during the D2 mission. This report concentrates on total dose measurements with TLDs during these mission. The results are discussed and compared to results of former missions and to calculations. Finally, dose equivalents and mean quality factors for each mission are presented which are derived from the TLD results and results obtained from the other detector systems. Dose equivalents range between 200 μSvd⁻¹ and 700 μSvd⁻¹.     

Psychosocial interactions during ISS missions

Based on anecdotal reports from astronauts and cosmonauts, studies of space analog environments on Earth, and our previous research on the Mir Space Station, a number of psychosocial issues have been identified that can lead to problems during long-duration space expeditions. Several of these issues were studied during a series of missions to the International Space Station. Using a mood and group climate questionnaire that was completed weekly by crewmembers in space and personnel in mission control, we found no evidence to support the presence of predicted decrements in well-being during the second half or in any specific quarter of the missions. The results did support the predicted displacement of negative feelings to outside supervisors among both crew and ground subjects. There were several significant differences in mood and group perceptions between Americans and Russians and between crewmembers and mission control personnel. Crewmembers related cohesion to the support role of their leader, and mission control personnel related cohesion to both the task and support roles of their leader. These findings are discussed with reference to future space missions.     

Future earth observation missions for oceanographic applications: Indian perspectives

Significant progress has been achieved in India in demonstrating the utility of remote sensing data for various oceanographic applications during the last one decade. Among these, techniques have been developed for retrieval of ocean surface waves, winds, wave forecast model, internal waves, sea surface temperature and chlorophyll pigments. Encouraged from these results as well as for meeting the specific and increasing data requirements on an assured basis by oceanographers, India is making concerted efforts for developing and launching state-of-the-art indigenous satellites for ocean applications in the coming years.

The first in the series of ocean satellites planned for launch is Oceansat-1 (IRS-P4) by early 1999. Oceansat-1 carries on-board an Ocean Colour Monitor (OCM) and a Multi-frequency Scanning Microwave Radiometer (MSMR). OCM will have 8 narrow spectral bands operating in visible and near- infrared bands (402–885 nm) with a spatial resolution of 360 m and swath of 1420 km. The MSMR with its all weather capability is configured to have measurements at 4 frequencies viz., 6.6, 10.65, 18 & 21 GHz in dual polarisation mode with a spatial resolution of 120, 80, 40 & 40 km, respectively with an overall swath of 1360 km. The Oceansat-1 with repetitivity of once in two days will provide global data for retrieval of various oceanographic and meteorological parameters such as chlorophyll (primary productivity), sea surface temperature and wind speed, besides a host of other parameters of relevance to meteorology.

A full fledged satellite for ocean applications known as Oceansat-2 (IRS-P7) is also planned for launch during 2002. This satellite with payload mix of microwave (Scatterometer, Altimeter & Passive Microwave Radiometer), Thermal (TIR) and Optical (OCM) sensors, will provide greater in-sight into the global understanding of ocean dynamics/resources. This mission is expected to provide a complete set of oceanographic measurements, which are useful for providing operational oceanographic services.

Efforts are also on towards development of missions having multi-frequency, multipolarisation and multi-look angle microwave payloads including Synthetic Aperture Radar (SAR) and advanced millimeter wave sounders, besides development of imaging spectrometers by 2005.

A well-knit plan has been initiated in India for utilisation of planned Oceansat data. Important efforts initiated in this direction include SATellite Coastal and Oceanographic Research and Ocean Information Services, which are being carried out on an integrated basis aiming at providing services to the down stream users. The paper highlights these efforts in India towards providing an operational ocean information services in the coming years.     

The case for small space missions

Three orders of arguments are outlined to illustrate the importance of small missions. First, the classical reasons (one has to begin small, educational aspects, introduction to the space field) are summarized; then some thoughts are introduced on the efficacy and the efficiency of the effort invested (how expensive is a national project, and how advantageous the inevitable multinational cooperation); finally, a synopsis of the considerations about the need for cultural changes in the space program (the challenge of the coming era, the resulting needs, the philosophy of “small missions” and its contributions) is given.     

Autonomous aerobraking for low-cost interplanetary missions

Aerobraking has previously been used to reduce the propellant required to deliver an orbiter to its desired final orbit. In principle, aerobraking should be possible around any target planet or moon having sufficient atmosphere to permit atmospheric drag to provide a portion of the mission ΔV, in lieu of supplying all of the required ΔV propulsively. The spacecraft is flown through the upper atmosphere of the target using multiple passes, ensuring that the dynamic pressure and thermal loads remain within the spacecraft's design parameters. NASA has successfully conducted aerobraking operations four times, once at Venus and three times at Mars. While aerobraking reduces the fuel required, it does so at the expense of time (typically 3–6 months), continuous Deep Space Network (DSN) coverage, and a large ground staff. These factors can result in aerobraking being a very expensive operational phase of the mission. However, aerobraking has matured to the point that much of the daily operation could potentially be performed autonomously onboard the spacecraft, thereby reducing the required ground support and attendant aerobraking related costs. To facilitate a lower-risk transition from ground processing to an autonomous capability, the NASA Engineering and Safety Center (NESC) has assembled a team of experts in aerobraking and interplanetary guidance and control to develop a high-fidelity, flight-like simulation. This simulation will be used to demonstrate the overall feasibility while exploring the potential for staff and DSN coverage reductions that autonomous aerobraking might provide. This paper reviews the various elements of autonomous aerobraking and presents an overview of the various models and algorithms that must be transformed from the current ground processing methodology to a flight-like environment. Additionally the high-fidelity flight software test bed, being developed from models used in a recent interplanetary mission, will be summarized.     

Optimal heliostationary missions of high-performance sailcraft

The aim of this paper is to provide a comprehensive and systematic study of optimal trajectories by characterizing sailcraft heliostationary orbits through the statement of a minimum-time problem. An indirect method is applied to calculate the control laws that minimize the mission time. An important contribution is a comparison of realistic with simplified (ideal) sail force models and an attempt is made to describe these models through a unified, compact formulation. Two cases are considered, that is the final heliostationary distance is left free or it is constrained to assume a specified value. Also, the problem is solved for both circular and elliptical parking orbits.     

Project Icarus: Optimisation of nuclear fusion propulsion for interstellar missions

The Daedalus spacecraft design was a two-stage configuration carrying 50,000 tonnes of DHe³ propellant. Daedalus was powered by electron driven Inertial Confinement Fusion (ICF) to implode the pellets at a frequency of 250 Hz. The mission was to Barnard's star 5.9 light years away in a duration of around 50 years. This paper is related to the successor Project Icarus, a theoretical engineering design study that began on 30 September 2009 and is a joint initiative between the Tau Zero Foundation and The British Interplanetary Society. In the first part of this paper, we explore ‘flyby’ variations on the Daedalus propellant utilisation for two different mission targets: Barnard's star and Epsilon Eridani, 10.7 light years away. With a fixed propellant mass a number of staged configurations (1–4) are derived for an optimal configuration but then moving to an off-optimal configuration due to the requirement for a high final science payload mass. Some comments are then made on the ICF pellet configuration compared to the typical pellets fielded at the National Ignition Facility (NIF) and those proposed for the Vista and Longshot fusion based propulsion designs. This is a working progress report, which aims to study perturbations of the Daedalus baseline design as part of a trade study. This is a submission of the Project Icarus Study Group.     

Psychology and culture during long-duration space missions

The objective of this paper is twofold: (a) to review the current knowledge of cultural, psychological, psychiatric, cognitive, interpersonal, and organizational issues that are relevant to the behavior and performance of astronaut crews and ground support personnel and (b) to make recommendations for future human space missions, including both transit and planetary surface operations involving the Moon or Mars. The focus will be on long-duration missions lasting at least six weeks, when important psychological and interpersonal factors begin to take their toll on crewmembers. This information is designed to provide guidelines for astronaut selection and training, in-flight monitoring and support, and post-flight recovery and re-adaptation.     

Contributions of the International Space Station towards future exploration missions

When the idea of a large space station in Low Earth Orbit (LEO) was conceived in the 1980s, it was primarily planned as an orbiting laboratory for microgravity research. Some even thought of it as an industrial plant in space. Whereas the latter did not materialize because of various reasons, the former is absolutely true when you talk about the International Space Station (ISS). Since the transition to a six astronaut crew in 2009 and the completion of its assembly in 2011, it has been intensively used as laboratory in a wide field of scientific topics. Experiments conducted on ISS have yielded first class results in biology, physiology, material science, basic physics, and many more. While its role as a laboratory in space is widely recognized, the awareness for its potential for preparing future exploration missions beyond LEO is just increasing. This paper provides information on how the ISS programme contributes to future exploration efforts, both manned and unmanned. It highlights the work that has been done or is currently underway in the fields of technology, operations, and science. Further potentials and future projects for exploration preparation are also shown. A special focus lies on experiments and projects primarily funded by the German Aerospace Center (DLR) or with strong German participation in the science team.     

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.     

Astromedicine and astrolaw: Emerging issues for advanced missions beyond Earth orbit

It is generally agreed within the scientific community that provision of appropriate medical facilities and administration of quality health care to astronauts are of great importance. However, for the more complex and remote missions envisaged for the future, issues of liability, responsibility and damage relating to medical practice may take on a greater significance and will need to be addressed. The author briefly reviews potential issues which may arise in the context of medical emergencies, crew autonomy and environmentally altered physiological status which characterize some projected advanced space missions and argues that the law of outer space will need to be expanded to take account of them.     

Critical issues in connection with human planetary missions: protection of and from the environment.

Activities associated with human missions to the Moon or to Mars will interact with the environment in two reciprocal ways: (i) the mission needs to be protected from the natural environmental elements that can be harmful to human health, the equipment or to their operations: (ii) the specific natural environment of the Moon or Mars should be protected so that it retains its value for scientific and other purposes. The following environmental elements need to be considered in order to protect humans and the equipment on the planetary surface: (i) cosmic ionizing radiation, (ii) solar particle events; (iii) solar ultraviolet radiation; (iv) reduced gravity; (v) thin atmosphere; (vi) extremes in temperatures and their fluctuations; (vii) surface dust; (viii) impacts by meteorites and micrometeorites. In order to protect the planetary environment. the requirements for planetary protection as adopted by COSPAR for lander missions need to be revised in view of human presence on the planet. Landers carrying equipment for exobiological investigations require special consideration to reduce contamination by terrestrial microorganisms and organic matter to the Greatest feasible extent. Records of human activities on the planet's surface should be maintained in sufficient detail that future scientific experimenters can determine whether environmental modifications have resulted from explorations. Grant numbers: 14056/99/NL/PA.     

Investigation of nuclear electric powered interstellar precursor missions

Nuclear Electric Propulsion (NEP) is a technology conceptually proposed since the 1940s by E. Stuhlinger in Germany. The JIMO mission originally planned by NASA in the early 2000s produced at least two designs of ion thrusters fed by a 20–30 kW nuclear powerplant. When compared to conventional (chemical) propulsion, the major advantage of NEP in the JIMO context was recognized to be the much higher I_sp (lab-tested at up to 15,000 s) and the capability for sustained power generation, up to 8–10 years when derated to I_sp about 8000 s.The goal of this paper is to show that current or near term NEP technology enables missions far beyond our immediate interplanetary backyard. In fact, by extending the semi-analytical approach used by Stuhlinger, with reasonable ratios α≡power/mass of the propulsion system (i.e., 0.1– 0.4 kW/kg), missions to the Kuiper Belt (40 AU and beyond) and even the so-called FOCAL mission (at 540 AU) become feasible with an attractive payload fraction and in times of order 10–15 years.Further results regarding missions to Sedna’s perihelion/aphelion, and to Oort’s cloud will also be presented, showing the constraints affecting their feasibility and mass budget.     

Risks of radiation cataracts from interplanetary space missions

Recognition of the human risks from radiation exposure during manned missions in deep space has been fostered by international co-operation; interagency collaboration is facilitating their evaluation. Further co-operation can lead, perhaps by the end of this decade, to an evaluation of one of the three major risks, namely radiation cataractogenesis, sufficient for use in the planning of the manned mission to Mars.