Satellite Image Compression Guided by Regions of Interest.

Small satellites empower different applications for an affordable price. By dealing with a limited capacity for using instruments with high power consumption or high data-rate requirements, small satellite missions usually focus on specific monitoring and observation tasks. Considering that multispectral and hyperspectral sensors generate a significant amount of data subjected to communication channel impairments, bandwidth constraint is an important challenge in data transmission. That issue is addressed mainly by source and channel coding techniques aiming at an effective transmission. This paper targets a significant further bandwidth reduction by proposing an on-the-fly analysis on the satellite to decide which information is effectively useful before coding and transmitting. The images are tiled and classified using a set of detection algorithms after defining the least relevant content for general remote sensing applications. The methodology makes use of the red-band, green-band, blue-band, and near-infrared-band measurements to perform the classification of the content by managing a cloud detection algorithm, a change detection algorithm, and a vessel detection algorithm. Experiments for a set of typical scenarios of summer and winter days in Stockholm, Sweden, were conducted, and the results show that non-important content can be identified and discarded without compromising the predefined useful information for water and dry-land regions. For the evaluated images, only 22.3% of the information would need to be transmitted to the ground station to ensure the acquisition of all the important content, which illustrates the merits of the proposed method. Furthermore, the embedded platform's constraints regarding processing time were analyzed by running the detection algorithms on Unibap's iX10-100 space cloud platform.

Phosphenes in low earth orbit: survey responses from 59 astronauts.

INTRODUCTION: It has long been known that many people in space experience sudden phosphenes, or light flashes. Although it is clear that they are related to high-energy particles in the space radiation environment, many details about them are still unknown. In an effort to gain more knowledge about the light flashes, a study was initiated to collect information from people who have recently flown in space. METHOD: A survey conducted by anonymous questionnaire was performed among astronauts regarding their experience of sudden light flashes in space. In all, 98 surveys were distributed to current NASA and ESA astronauts. RESULTS: Among the 59 respondents, 47 noticed them sometime during spaceflight. Most often they were noted before sleep, and several people even thought the light flashes disturbed their sleep. The light flashes predominantly appear white, have elongated shapes, and most interestingly, often come with a sense of motion. The motion is described as sideways, diagonal, or in-out, but never in the vertical direction. DISCUSSION: Comparisons with earlier studies of light flashes in space and several ground-based studies during the 1970s are made. One interesting observation from this is that it seems that a small fraction of the light flashes is caused by Cherenkov radiation, while the majority is probably caused by some kind of direct interaction with elements in the retina.

The Sileye-3/Alteino experiment for the study of light flashes, radiation environment and astronaut brain activity on board the International Space Station.

In this work we describe the instrument Sileye-3/Alteino, placed on board the International Space Station in April 2002. The instrument is constituted by an Electroencephalograph and a cosmic ray silicon detector. The scientific aims include the investigation of the Light Flash phenomenon, the measurement of the radiation environment and the nuclear abundance inside the ISS and the study of astronaut brain activity in space when subject to cosmic rays.