Spatial heterogeneity in the radiogenic activity of the lunar interior: Inferences from CHACE and LLRI on Chandrayaan-1

In the past, clues on the potential radiogenic activity of the lunar interior have been obtained from the isotopic composition of noble gases like Argon. Excess Argon (40) relative to Argon (36), as compared to the solar wind composition, is generally ascribed to the radiogenic activity of the lunar interior. Almost all the previous estimates were based on, ‘on-the-spot’ measurements from the landing sites. Relative concentration of the isotopes of ⁴⁰Ar and ³⁶Ar along a meridian by the Chandra’s Altitudinal Composition Explorer (CHACE) experiment, on the Moon Impact Probe (MIP) of India’s first mission to Moon, has independently yielded clues on the possible spatial heterogeneity in the radiogenic activity of the lunar interior in addition to providing indicative ‘antiquity’ of the lunar surface along the ground track over the near side of the moon. These results are shown to broadly corroborate the independent topography measurements by the Lunar Laser Ranging Instrument (LLRI) in the main orbiter Chandrayaan-1. The unique combination of these experiments provided high spatial resolution data while indicating the possible close linkages between the lunar interior and the lunar ambience.     

Height of shock formation in the solar corona inferred from observations of type II radio bursts and coronal mass ejections

Employing coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25–40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.     

Concept of wireless sensor network for future in-situ exploration of lunar ice using wireless impedance sensor

It is known that a wireless sensor network uses some sort of sensors to detect a physical quantity of interest, in general. The wireless sensor network is a potential tool for exploring the difficult-to-access area on the earth and the concept may be extended to space applications in future. Recently, lunar water has been detected by a few lunar missions using remote sensing techniques. The lunar water is expected to be in the form of ice at very low temperatures of permanently dark regions on the moon. To support the remote observations and also to find out potential ice bearing sites on the moon, in-situ measurement of the lunar ice is essential. However, a rover may not be able to reach the permanently shadowed regions due to terrain irregularity. One possibility to access such areas is to use a wireless sensor network on the lunar surface.     

Preparation of the Biochip experiment on the EXPOSE-R2 mission outside the International Space Station

Biochips might be suited for planetary exploration. Indeed, they present great potential for the search for biomarkers – molecules that are the sign of past or present life in space – thanks to their size (miniaturized devices) and sensitivity. Their detection principle is based on the recognition of a target molecule by affinity receptors fixed on a solid surface. Consequently, one of the main concerns when developing such a system is the behavior of the biological receptors in a space environment. In this paper, we describe the preparation of an experiment planned to be part of the EXPOSE-R2 mission, which will be conducted on the EXPOSE-R facility, outside the International Space Station (ISS), in order to study the resistance of biochip models to space constraints (especially cosmic radiation and thermal cycling). This experiment overcomes the limits of ground tests which do not reproduce exactly the space parameters. Indeed, contrary to ground experiments where constraints are applied individually and in a limited time, the biochip models on the ISS will be exposed to cumulated constraints during several months. Finally, this ISS experiment is a necessary step towards planetary exploration as it will help assessing whether a biochip can be used for future exploration missions.     

New evidence of solar variation in temperature proxies from Northern Fennoscandia

A new summer temperature proxy was built for northern Fennoscandia in AD 1000–2004 using parameters of tree growth from a large region, extending from the Swedish Scandes to the Kola Peninsula. It was found that century-scale (55–140 year) cyclicity is present in this series during the entire time interval. This periodicity is highly significant and has a bi-modal structure, i.e. it consists of two oscillation modes, 55–100 year and 100–140 year variations. A comparison of the century-long variation in the northern Fennoscandian temperature proxy with the corresponding variations in Wolf numbers and concentration of cosmogenic ¹⁰Be in glacial ice shows that a probable cause of this periodicity is the modulation of regional climate by the secular solar cycle of Gleissberg. This is in line with the results obtained previously for a more limited part of the region (Finnish Lapland: 68–70° N, 20–30° E). Thus the reality of a link between long-term changes in solar activity and climate in Fennoscandia has been confirmed. Possible mechanisms of solar influence on the lower troposphere are discussed.     

Evaluation of upper body muscle activity during cardiopulmonary resuscitation performance in simulated microgravity

Performance of efficient single-person cardiopulmonary resuscitation (CPR) is vital to maintain cardiac and cerebral perfusion during the 2–4 min it takes for deployment of advanced life support during a space mission. The aim of the present study was to investigate potential differences in upper body muscle activity during CPR performance at terrestrial gravity (+1Gz) and in simulated microgravity (μG). Muscle activity of the triceps brachii, erector spinae, rectus abdominis and pectoralis major was measured via superficial electromyography in 20 healthy male volunteers. Four sets of 30 external chest compressions (ECCs) were performed on a mannequin. Microgravity was simulated using a body suspension device and harness; the Evetts–Russomano (ER) method was adopted for CPR performance in simulated microgravity. Heart rate and perceived exertion via Borg scores were also measured. While a significantly lower depth of ECCs was observed in simulated microgravity, compared with +1Gz, it was still within the target range of 40–50 mm. There was a 7.7% decrease of the mean (±SEM) ECC depth from 48 ± 0.3 mm at +1Gz, to 44.3 ± 0.5 mm during microgravity simulation (p < 0.001). No significant difference in number or rate of compressions was found between the two conditions. Heart rate displayed a significantly larger increase during CPR in simulated microgravity than at +1Gz, the former presenting a mean (±SEM) of 23.6 ± 2.91 bpm and the latter, 76.6 ± 3.8 bpm (p < 0.001). Borg scores were 70% higher post-microgravity compressions (17 ± 1) than post +1Gz compressions (10 ± 1) (p < 0.001). Intermuscular comparisons showed the triceps brachii to have significantly lower muscle activity than each of the other three tested muscles, in both +1Gz and microgravity. As shown by greater Borg scores and heart rate increases, CPR performance in simulated microgravity is more fatiguing than at +1Gz. Nevertheless, no significant difference in muscle activity between conditions was found, a result that is favourable for astronauts, given the inevitable muscular and cardiovascular deconditioning that occurs during space travel.     

Some issues of time-optimal control over a spacecraft programmed turn

The problem of optimal turn of a spacecraft from an arbitrary initial position to a final specified angular position in a minimum time is considered and solved. A case is investigated, when the constraint on spacecraft’s angular momentum during the turn is essential. Based on the quaternion method a solution to the posed problem has been found, and an optimal control program is constructed taking the constraints on controlling moment into account. The optimal control is found in the class of regular motions. A condition (calculation expression) is presented for determining the moment to begin braking with the use of measurements of current motion parameters, which considerably improves the accuracy of putting the spacecraft into a preset position. For a dynamically symmetrical spacecraft the solution to the problem of optimal control by the spacecraft spatial turn is presented in analytical form (expressions in elementary functions). An example of mathematical modeling of the spacecraft motion dynamics under optimal control over reorientation is given.     

A new universal equation for the time of transfer between two points of the central gravitational field

The paper presents the derivation of two new equations for calculating the time of transfer between two points of the central gravitational field: for hyperbolic orbits and the universal equation for elliptical and hyperbolic orbits. In the paper we have used as an independent variable, instead of the linear elements (semimajor axis, focal parameter of orbit or a chord connecting the ends of boundary radii of transfer), the angular parameter—the angle between the radius vector of an initial point of transfer and the vector of initial velocity of transfer. Paper’s material is a continuation of that presented in the “Space research“ Journal, vol. 2, March–April, 2009.