The OSIRIS-REx Camera Suite (OCAMS) will acquire images essential to collecting a sample from the surface of Bennu. During proximity operations, these images will document the presence of satellites and plumes, record spin state, enable an accurate model of the asteroid's shape, and identify any surface hazards. They will confirm the presence of sampleable regolith on the surface, observe the sampling event itself, and image the sample head in order to verify its readiness to be stowed. They will document Bennu's history as an example of early solar system material, as a microgravity body with a planetesimal size- scale, and as a carbonaceous object. OCAMS is fitted with three cameras. The MapCam will record color images of Bennu as a point source on approach to the asteroid in order to connect Bennu's ground-based point-source observational record to later higher-resolution surface spectral imaging. The SamCam will document the sample site before, during, and after it is disturbed by the sample mechanism. The PolyCam, using its focus mechanism, will observe the sample site at sub-centimeter resolutions, revealing surface texture and morphology. While their imaging requirements divide naturally between the three cameras, they preserve a strong degree of functional overlap. OCAMS and the other spacecraft instruments will allow the OSIRIS-REx mission to collect a sample from a microgravity body on the same visit during which it was first optically acquired from long range, a useful capability as humanity reaches out to explore near-Earth, Main-Belt and Jupiter Trojan asteroids.

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Challenging space missions include those at very low altitudes, where the atmosphere is source of aerodynamic drag on the spacecraft. To extend such missions lifetime, an efficient propulsion system is required. One solution is Atmosphere-Breathing Electric Propulsion (ABEP). It collects atmospheric particles to be used as propellant for an electric thruster. The system would minimize the requirement of limited propellant availability and can also be applied to any planet with atmosphere, enabling new mission at low altitude ranges for longer times. Challenging is also the presence of reactive chemical species, such as atomic oxygen in Earth orbit. Such species cause erosion of (not only) propulsion system components, i.e. acceleration grids, electrodes, and discharge channels of conventional EP systems. IRS is developing within the DISCOVERER project, an intake and a thruster for an ABEP system. The paper describes the design and implementation of the RF helicon-based inductive plasma thruster (IPT). This

The rates of elimination of primary, secondary and tertiary a-hydroxycarboxylic acids were determined in a seasoned, static reaction vessel over the temperature range 280-390 OC and the pressure range 30-201 Tom. The reactions, in the presence of a free radical inhibitor, are homogeneous, unimolecular and follow a first-order rate law. The rate coefficients are given b the following equations: for Flycolic acid, log k1 (s-') = (14.03 It 0.24) -(209.3 4 1.5) kJmol-'(2.30387')-'; for lactic acid, lo k~ (s-) = (12.24 It 0.11) -(182.8 It 1.3) kJmol-' (2*30317')-'; and for ease with which the hydroxy group is removed from primary to tertiary a-hydroxycarboxylk acids are reflected in rate enhancement. The mechanism of these eliminations appears to proceed through a semi-polar Bve-membered cyclic transition state.2-hydroxyisobutyric acid, log k~ (s-k ) = (12-91 -C 0-13) -(174.7 f 1.5) W mol-' (2*303R7')-'. The basicity and the

The kinetics of the gas‐phase elimination of several 2‐substituted primary, secondary and tertiary hydroxy groups in nitroalkanes were determined in a static reaction system over the temperature range 220–400°C and pressure range of 29–235 Torr. The reactions, in seasoned vessels, are homogeneous and unimolecular and obey a first‐order rate law. The presence of secondary and tertiary hydroxy substituent at the 2‐position of the nitro group in nitroalkanes leads to a retro‐aldol type of decomposition. The mechanism may be rationalized in terms of a six‐membered cyclic transition state to give the corresponding aldehyde or ketone and the nitroalkane, respectively. However, some of the primary 2‐hydroxy groups in nitroalkanes undergo a dehydration process with very limited isomerization to the corresponding alkyl nitrate. The mechanism of dehydration is believed to proceed through a six‐membered rather than the already reported four‐membered cyclic transition state to give the nitroalkene and water. In the case of the primary hydroxy substituent in 2‐methyl‐2‐nitro‐1‐pentanol, the products of elimination are HNO2 gas and 3‐hydroxy‐2‐methyl‐1‐propene. This reaction is rationalized in terms of a four‐membered cyclic transition state type of mechanism. The kinetic and thermodynamic parameters of the hydroxynitroalkane substrates are presented and discussed. Copyright © 2004 John Wiley & Sons, Ltd.