Calibrating Geosynchronous and Polar Orbiting Satellites: Sharing Best Practices

Earth remote sensing optical satellite systems are often divided into two categories—geosynchronous and sun-synchronous. Geosynchronous systems essentially rotate with the Earth and continuously observe the same region of the Earth. Sun-synchronous systems are generally in a polar orbit and view differing regions of the Earth at the same local time. Although similar in instrument design, there are enough differences in these two types of missions that often the calibration of the instruments can be substantially different. Thus, respective calibration teams develop independent methods and do not interact regularly or often. Yet, there are numerous areas of overlap and much to learn from one another. To address this issue, a panel of experts from both types of systems was convened to discover common areas of concern, areas where improvements can be made, and recommendations for the future. As a result of the panelist’s efforts, a set of eight recommendations were developed. Those that are related to improvements of current technologies include maintaining sun-synchronous orbits (not allowing orbital decay), standardization of spectral bandpasses, and expanded use of well-developed calibration techniques such as deep convective clouds, pseudo invariant calibration sites, and lunar methodologies. New techniques for expanded calibration capability include using geosynchronous instruments as transfer radiometers, continued development of ground-based prelaunch calibration technologies, expansion of RadCalNet, and development of space-based calibration radiometer systems.

Explicit Communication Among Stigmergic Robots

In this paper, we investigate avenues for the exchange of information (explicit communication) among deaf and mute mobile robots scattered in the plane. We introduce the use of movement-signals (analogously to flight signals and bees waggle) as a mean to transfer messages, enabling the use of distributed algorithms among robots. We propose one-to-one deterministic movement protocols that implement explicit communication among semi-synchronous robots. We first show how the movements of robots can provide implicit acknowledgment in semi-synchronous systems. We use this result to design one-to-one communication among a pair of robots. Then, we propose two one-to-one communication protocols for any system of [Formula: see text] robots. The former works for robots equipped with observable IDs that agree on a common direction (sense of direction). The latter enables one-to-one communication assuming robots devoid of any observable IDs or sense of direction. All protocols (for either two or any number of robots) assume that no robot remains inactive forever. However, they cannot avoid that the robots move either away or closer to each others, by the way requiring robots with an infinite visibility. In this paper, we also present how to overcome these two disadvantages (some activity of every robot and infinite visibility). Our protocols enable the use of distributing algorithms based on message exchanges among swarms of stigmergic robots. They also allow robots to be equipped with the means of communication to tolerate faults in their communication devices.

Typical Design of Synchronous Controller to Minimize Response Time and Power

As power dissipation and time constraint have become vital challenges during the creation of a digital circuit, researchers' and designers' efforts have increased to figure out new ways of preserving power through the study of its sources and its impacts as well as through the decrease of response time to obtain faster treatments. However, it is widely acknowledged that these two parameters are antagonistic in synchronous systems. In fact, current technologies have managed to further decrease the response time to have a faster circuit at the cost of a considerable simultaneous augmentation in its power or vice versa, which leaves no option for designers but to choose from these two important parameters. Hence, the main objective of this chapter is to propose a design method that simultaneously builds a low power design and provides a faster circuit. For the achievement of that purpose, a controller based on a finite state machine (FSM) has been chosen as an example of synchronous system to prove that the new proposed design can optimize both parameters: time and power.