Temperature comparison between CHAMP radio occultation and TIMED/SABER measurements in the lower stratosphere

Global Positioning System (GPS) receiver on the CHAllenging Mini-satellite Payload (CHAMP) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, one of four on board the TIMED satellite, provide middle atmosphere temperature profiles by Radio Occultation (RO) and limb viewing infrared emission measurements, respectively. These temperature profiles retrieved by two different techniques in the stratosphere are compared with each other using more than 1300 correlative profiles in March, September and December 2005. The over-all mean differences averaged over 15 and 35 km are approximately −2 K and standard deviation is less than 3 K. Below 20 km of altitude, relatively small mean temperature differences ∼1 K are observed in wide latitudinal range except for June (during the SABER nighttime observation). In the middle to low latitudes, between 30°S and 30°N, the temperature difference increases with height from ∼0–1 K at 15 km, to ∼−4 K at 35 km of altitude. Large temperature differences about −4 to −6 K are observed between 60°S and 30°N and 31–35 km of altitude for all months and between 0° and 30°N below 16 km during June (nighttime).     

A high quality low state observation of Cir X-1

Cir X-1 was extremely faint when we observed it with EXOSAT. The light curve clearly shows the source in two states; a faint variable state and a very faint but more constant state. The spectrum is very complicated but clearly shows the existence of an iron line.     

Variations of the solar acoustic high-degree mode frequencies over solar cycle 23

Using full-disk observations obtained with the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) spacecraft, we present variations of the solar acoustic mode frequencies caused by the solar activity cycle. High-degree (100 < ? < 900) solar acoustic modes were analyzed using global helioseismology analysis techniques over most of solar cycle 23. We followed the methodology described in details in [Korzennik, S.G., Rabello-Soares, M.C., Schou, J. On the determination of Michelson Doppler Imager high-degree mode frequencies. ApJ 602, 481–515, 2004] to infer unbiased estimates of high-degree mode parameters ([see also Rabello-Soares, M.C., Korzennik, S.G., Schou, J. High-degree mode frequencies: changes with solar cycle. ESA SP-624, 2006]). We have removed most of the known instrumental and observational effects that affect specifically high-degree modes. We show that the high-degree changes are in good agreement with the medium-degree results, except for years when the instrument was highly defocused. We analyzed and discuss the effect of defocusing on high-degree estimation. Our results for high-degree modes confirm that the frequency shift scaled by the relative mode inertia is a function of frequency and it is independent of degree.     

Influence of climatic operational conditions of a helicopter on physico-mechanical properties of composite materials

The results of numerical and experimental study of physico-mechanical properties of composite materials are proposed and variations in rigidity characteristics of the hub working part of the hingeless type within the entire range of helicopter operational temperatures are evaluated.     

ARTEMIS Mission Design

The ARTEMIS mission takes two of the five THEMIS spacecraft beyond their prime mission objectives and reuses them to study the Moon and the lunar space environment. Although the spacecraft and fuel resources were tailored to space observations from Earth orbit, sufficient fuel margins, spacecraft capability, and operational flexibility were present that with a circuitous, ballistic, constrained-thrust trajectory, new scientific information could be gleaned from the instruments near the Moon and in lunar orbit. We discuss the challenges of ARTEMIS trajectory design and describe its current implementation to address both heliophysics and planetary science objectives. In particular, we explain the challenges imposed by the constraints of the orbiting hardware and describe the trajectory solutions found in prolonged ballistic flight paths that include multiple lunar approaches, lunar flybys, low-energy trajectory segments, lunar Lissajous orbits, and low-lunar-periapse orbits. We conclude with a discussion of the risks that we took to enable the development and implementation of ARTEMIS.     

Command Link Encoder for Gemini Rendezvous

The first application of a magnetic encoder in a space-to-space command link was proven successful in the Gemini rendezvous missions. The functional aspects of the command link and the mechanization of the encoder are described.