Advanced Technologies Demonstrated by the Miniature Integrated Camera and Spectrometer (MICAS) Aboard Deep Space 1

MICAS is an integrated multi-channel instrument that includes an ultraviolet imaging spectrometer (80–185 nm), two high-resolution visible imagers (10–20 μrad/pixel, 400–900 nm), and a short-wavelength infrared imaging spectrometer (1250–2600 nm). The wavelength ranges were chosen to maximize the science data that could be collected using existing semiconductor technologies and avoiding the need for multi-octave spectrometers. It was flown on DS1 to validate technologies derived from the development of PICS (Planetary Imaging Camera Spectrometer). These technologies provided a novel systems approach enabling the miniaturization and integration of four instruments into one entity, spanning a wavelength range from the UV to IR, and from ambient to cryogenic temperatures with optical performance at a fraction of a wavelength. The specific technologies incorporated were: a built-in fly-by sequence; lightweight and ultra-stable, monolithic silicon-carbide construction, which enabled room-temperature alignment for cryogenic (85–140 K) performance, and provided superb optical performance and immunity to thermal distortion; diffraction-limited, shared optics operating from 80 to 2600 nm; advanced detector technologies for the UV, visible and short-wavelength IR; high-performance thermal radiators coupled directly to the short-wave infrared (SWIR) detector optical bench, providing an instrument with a mass less than 10 kg, instrument power less than 10 W, and total instrument cost of less than ten million dollars. The design allows the wavelength range to be extended by at least an octave at the short wavelength end and to ∼50 microns at the long wavelength end. Testing of the completed instrument demonstrated excellent optical performance down to 77 K, which would enable a greatly reduced background for longer wavelength detectors. During the Deep Space 1 Mission, MICAS successfully collected images and spectra for asteroid 9969 Braille, Mars, and comet 19/P Borrelly. The Borrelly encounter was a scientific hallmark providing the first clear, high resolution images and excellent, short-wavelength infrared spectra of the surface of an active comet’s nucleus.     

The Magnetometer Instrument on MESSENGER

The Magnetometer (MAG) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is a low-noise, tri-axial, fluxgate instrument with its sensor mounted on a 3.6-m-long boom. The boom was deployed on March 8, 2005. The primary MAG science objectives are to determine the structure of Mercury’s intrinsic magnetic field and infer its origin. Mariner 10 observations indicate a planetary moment in the range 170 to 350 nT R _M³ (where R _M is Mercury’s mean radius). The uncertainties in the dipole moment are associated with the Mariner 10 trajectory and variability of the measured field. By orbiting Mercury, MESSENGER will significantly improve the determination of dipole and higher-order moments. The latter are essential to understanding the thermal history of the planet. MAG has a coarse range, ±51,300 nT full scale (1.6-nT resolution), for pre-flight testing, and a fine range, ±1,530 nT full scale (0.047-nT resolution), for Mercury operation. A magnetic cleanliness program was followed to minimize variable and static spacecraft-generated fields at the sensor. Observations during and after boom deployment indicate that the fixed residual field is less than a few nT at the location of the sensor, and initial observations indicate that the variable field is below 0.05 nT at least above about 3 Hz. Analog signals from the three axes are low-pass filtered (10-Hz cutoff) and sampled simultaneously by three 20-bit analog-to-digital converters every 50 ms. To accommodate variable telemetry rates, MAG provides 11 output rates from 0.01 s⁻¹ to 20 s⁻¹. Continuous measurement of fluctuations is provided with a digital 1–10 Hz bandpass filter. This fluctuation level is used to trigger high-time-resolution sampling in eight-minute segments to record events of interest when continuous high-rate sampling is not possible. The MAG instrument will provide accurate characterization of the intrinsic planetary field, magnetospheric structure, and dynamics of Mercury’s solar wind interaction.     

The Genesis Solar Wind Concentrator

The primary goal of the Genesis Mission is to collect solar wind ions and, from their analysis, establish key isotopic ratios that will help constrain models of solar nebula formation and evolution. The ratios of primary interest include ¹⁷O/¹⁶O and ¹⁸O/¹⁶O to ±0.1%, ¹⁵N/¹⁴N to ±1%, and the Li, Be, and B elemental and isotopic abundances. The required accuracies in N and O ratios cannot be achieved without concentrating the solar wind and implanting it into low-background target materials that are returned to Earth for analysis. The Genesis Concentrator is designed to concentrate the heavy ion flux from the solar wind by an average factor of at least 20 and implant it into a target of ultra-pure, well-characterized materials. High-transparency grids held at high voltages are used near the aperture to reject >90% of the protons, avoiding damage to the target. Another set of grids and applied voltages are used to accelerate and focus the remaining ions to implant into the target. The design uses an energy-independent parabolic ion mirror to focus ions onto a 6.2 cm diameter target of materials selected to contain levels of O and other elements of interest established and documented to be below 10% of the levels expected from the concentrated solar wind. To optimize the concentration of the ions, voltages are constantly adjusted based on real-time solar wind speed and temperature measurements from the Genesis ion monitor. Construction of the Concentrator required new developments in ion optics; materials; and instrument testing and handling. This revised version was published online in August 2006 with corrections to the Cover Date.     

The paradoxes of space

‘Space — the commercial opportunities’, an international business strategy conference, London, UK, 31 October–1 November 1984, organized by Online Conferences Ltd, Pinner Green House, Ash Hill Drive, Pinner HA5 2AE, Middlesex, UK.     

Lithopanspermia in star-forming clusters

This paper considers the lithopanspermia hypothesis in star-forming groups and clusters, where the chances of biological material spreading from one solar system to another is greatly enhanced (relative to action in the field) because of the close proximity of the systems and lower relative velocities. These effects more than compensate for the reduced time spent in such crowded environments. This paper uses approximately 300,000 Monte Carlo scattering calculations to determine the cross sections for rocks to be captured by binaries and provides fitting formulae for other applications. We assess the odds of transfer as a function of the ejection speed v (eject) and number N(.) of members in the birth aggregate. The odds of any given ejected meteoroid being recaptured by another solar system are relatively low, about 1:10(3)-10(6) over the expected range of ejection speeds and cluster sizes. Because the number of ejected rocks (with mass m > 10 kg) per system can be large, N (R) approximately 10(16), virtually all solar systems are likely to share rocky ejecta with all of the other solar systems in their birth cluster. The number of ejected rocks that carry living microorganisms is much smaller and less certain, but we estimate that N (B) approximately 10(7) rocks can be ejected from a biologically active solar system. For typical birth environments, the capture of life-bearing rocks is expected to occur N (bio) asymptotically equal to 10-16,000 times (per cluster), depending on the ejection speeds. Only a small fraction (f (imp) approximately 10(4)) of the captured rocks impact the surfaces of terrestrial planets, so that N (lps) asymptotically equal to 10(3)-1.6 lithopanspermia events are expected per cluster (under favorable conditions). Finally, we discuss the question of internal versus external seeding of clusters and the possibility of Earth seeding young clusters over its biologically active lifetime.     

Tírez lake as a terrestrial analog of Europa

Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for microbial detection and characterization in hypersaline environments makes this methodology strongly advisable for future Europa astrobiological missions.     

Ozone concentrations and ultraviolet fluxes on Earth-like planets around other stars

Coupled radiative-convective/photochemical modeling was performed for Earth-like planets orbiting different types of stars (the Sun as a G2V, an F2V, and a K2V star). O(2) concentrations between 1 and 10(-5) times the present atmospheric level (PAL) were simulated. The results were used to calculate visible/near-IR and thermal-IR spectra, along with surface UV fluxes and relative dose rates for erythema and DNA damage. For the spectral resolution and sensitivity currently planned for the first generation of terrestrial planet detection and characterization missions, we find that O(2) should be observable remotely in the visible for atmospheres containing at least 10(-2) PAL of O(2). O(3) should be visible in the thermal-IR for atmospheres containing at least 10(-3) PAL of O(2). CH(4) is not expected to be observable in 1 PAL O(2) atmospheres like that of modern Earth, but it might be observable at thermal-IR wavelengths in "mid-Proterozoic-type" atmospheres containing approximately 10(-1) PAL of O(2). Thus, the simultaneous detection of both O(3) and CH(4) - considered to be a reliable indication of life - is within the realm of possibility. High-O(2) planets orbiting K2V and F2V stars are both better protected from surface UV radiation than is modern Earth. For the F2V case the high intrinsic UV luminosity of the star is more than offset by the much thicker ozone layer. At O(2) levels below approximately 10(-2) PAL, planets around all three types of stars are subject to high surface UV fluxes, with the F2V planet exhibiting the most biologically dangerous radiation environment. Thus, while advanced life is theoretically possible on high-O(2) planets around F stars, it is not obvious that it would evolve as it did on Earth.     

Measuring Techniques Applied in an MHD-Augmented Shock Tunnel

The determination of the detailed performance of an MHD-augmented high-enthalphy shock tunnel requires the simultaneous measurment of a large number of aerodynamic, electrical, and electromagnetic parameters in a test time interval of the order of several hundred microseconds. In the feasibility study currently being conducted in our laboratory of such a device, an extensive measuring system was set up and evaluated, and is being used to acquire facility performance data. This paper describes this measuring system, discusses the modifications and adaptations applied to make the various components of the system operable and compatible, and gives illustrative examples of the performance of the system.     

Antarctic meteor observations using the Davis MST and meteor radars

This paper presents the meteor observations obtained using two radars installed at Davis (68.6°S, 78.0°E), Antarctica. The Davis MST radar was installed primarily for observation of polar mesosphere summer echoes, with additional transmit and receive antennas installed to allow all-sky interferometric meteor radar observations. The Davis meteor radar performs dedicated all-sky interferometric meteor radar observations. The annual count rate variation for both radars peaks in mid-summer and minimizes in early Spring. The height distribution shows significant annual variation, with minimum (maximum) peak heights and maximum (minimum) height widths in early Spring (mid-summer). Although the meteor radar count rate and height distribution variations are consistent with a similar frequency meteor radar operating at Andenes (69.3°N), the peak heights show a much larger variation than at Andenes, while the count rate maximum-to-minimum ratios show a much smaller variation. Investigation of the effects of the temporal sampling parameters suggests that these differences are consistent with the different temporal sampling strategies used by the Davis and Andenes meteor radars. The new radiant mapping procedure of [Jones, J., Jones, W., Meteor radiant activity mapping using single-station radar observations, Mon. Not. R. Astron. Soc., 367(3), 1050–1056, doi: 10.1111/j.1365-2966.2006.10025.x, 2006] is investigated. The technique is used to detect the Southern delta-Aquarid meteor shower, and a previously unknown weak shower. Meteoroid speeds obtained using the Fresnel transform are presented. The diurnal, annual, and height variation of meteoroid speeds are presented, with the results found to be consistent with those obtained using specular meteor radars. Meteoroid speed estimates for echoes identified as Southern delta-Aquarid and Sextantid meteor candidates show good agreement with the theoretical pre-atmospheric speeds of these showers (41 km s⁻¹ and 32 km s⁻¹, respectively). The meteoroid speeds estimated for these showers show decreasing speed with decreasing height, consistent with the effects of meteoroid deceleration. Finally, we illustrate how the new radiant mapping and meteoroid speed techniques can be combined for unambiguous meteor shower detection, and use these techniques to detect a previously unknown weak shower.