An Atmospheric Origin for HCN-Derived Polymers on Titan

Titan’s haze is strongly suspected to be an HCN-derived polymer, but despite the first in situ measurements by the ESA-Huygens space probe, its chemical composition and formation process remain largely unknown. To investigate this question, we simulated the atmospheric haze formation process, experimentally. We synthesized analogues of Titan’s haze, named Titan tholins, in an irradiated N2–CH4 gas mixture, mimicking Titan’s upper atmosphere chemistry. HCN was monitored in situ in the gas phase simultaneously with the formation and evolution of the haze particles. We show that HCN is produced as long as the particles are absent, and is then progressively consumed when the particles appear and grow. This work highlights HCN as an effective precursor of Titan’s haze and confirms the HCN-derived polymer nature of the haze.

AN ARTIFICIAL EXPERIMENT AIMED TO SPECIFY THE GRAVITY LAW IN THE SOLAR SYSTEM

Ultra-sensitivity of a planet’s gravity assist (GA) to changes of the test-body impact parameter prompts a space experiment testing the nature of gravitational field in the Solar system. The Sun, Earth and Venus serve as the space lab with a primitive space probe (ball) as a test body moving on a ballistic trajectory from the Earth to Venus (rendering GA) and backwards to the Earth’s orbit. We show that in Newton and Einstein gravity, the probe’s final positions (reached at the same time) may differ greatly; an Earth’s observer can measure the gap.

Inter-Calibration of the OSIRIS-REx NavCams with Earth-Viewing Imagers

The Earth-viewed images acquired by the space probe OSIRIS-REx during its Earth gravity assist flyby maneuver on 22 September 2017 provided an opportunity to radiometrically calibrate the onboard NavCam imagers. Spatially-, temporally-, and angularly-matched radiances from the Earth viewing GOES-15 and DSCOVR-EPIC imagers were used as references for deriving the calibration gain of the NavCam sensors. An optimized all-sky tropical ocean ray-matching (ATO-RM) calibration approach that accounts for the spectral band differences, navigation errors, and angular geometry differences between NavCam and the reference imagers is formulated in this paper. Prior to ray-matching, the GOES-15 and EPIC pixel level radiances were mapped into the NavCam field of view. The NavCam 1 ATO-RM gain is found to be 9.874 × 10−2 Wm−2sr−1µm−1DN−1 with an uncertainty of 3.7%. The ATO-RM approach predicted an offset of 164, which is close to the true space DN of 170. The pre-launch NavCam 1 and 2 gains were compared with the ATO-RM gain and were found to be within 2.1% and 2.8%, respectively, suggesting that sensor performance is stable in space. The ATO-RM calibration was found to be consistent within 3.9% over a factor of ±2 NavCam 2 exposure times. This approach can easily be adapted to inter-calibrate other space probe cameras given the current constellation of geostationary imagers.

Radio and Telecommunications

The Cassini space probe and its recent voyage to Saturn, and communications system are described. Communication with it at the speed of light takes over an hour to reach Earth. The power and range of its transmitter, how its antenna works, and NASA’s deep space communications global network. Heinrich Hertz and the discovery of radio communication in 1887, after Maxwell’s death. FitzGerald’s publication predicting radio transmission in 1883. His life and apprenticeship under Helmholtz and theoretical and experimental work. His use of a spark gap as a receiver with resonant circuits to set up standing electro-magnetic waves in his laboratory. His discovery that these waves, of much lower frequency than light, travelled at the speed of light. Dipole radiation. Hertz’s visit to London and his life. David Hughes, his life, adventures and inventions, including the carbon microphone and printing telegraph, and his accidental pre-discovery of radio using a carbon microphone as a “coherer” detector.

Single-Bus and Dual-Bus Architectures of Electrical Power Systems for Small Spacecraft

Nowadays, it has become possible for universities and new businesses to launch satellites of reduced size and cost fulfilling viable missions. Nevertheless, there is still a considerable failure rate that reduces the expected lifetime of these spacecraft. One of the main causes of failure is the power system. Redundancy is one of the main options to enhance its lifetime and lower the failure rate. However, cost, mass, and complexity increase due to redundancy, making it more difficult to complete the projects. Thus, it is necessary to enhance the lifetime of power systems while keeping the development process simple and fast. This paper proposes two configurations of an electrical power system with duplicate components: single-bus configuration has been designed for a nanosatellite not yet launched and dual-bus configuration for a micro deep-space probe launched into a heliocentric orbit. The design and implementation of two dual electrical power systems are described; measurements and on-orbit data of the electrical power system of the micro deep-space probe are also presented, demonstrating that the dual-bus electrical power system can be successfully used in spacecraft. Lastly, conclusions regarding the redundancy considerations for small satellite electrical power systems are drawn based on these two examples.