Low cost satellite constellations for nearly continuous global coverage

Abstract

Satellite services are fundamental to the global economy, and their design reflects a tradeoff between coverage and cost. Here, we report the discovery of two alternative 4-satellite constellations with 24- and 48-hour periods, both of which attain nearly continuous global coverage. The 4-satellite constellations harness energy from nonlinear orbital perturbation forces (e.g., Earth’s geopotential, gravitational effects of the sun and moon, and solar radiation pressure) to reduce their propellant and maintenance costs. Our findings demonstrate that small sacrifices in global coverage at user-specified longitudes allow operationally viable constellations with significantly reduced mass-to-orbit costs and increased design life. The 24-hour period constellation reduces the overall required vehicle mass budget for propellant by approximately 60% compared to a geostationary Earth orbit constellation with similar coverage over typical satellite lifetimes. Mass savings of this magnitude permit the use of less expensive launch vehicles, installation of additional instruments, and substantially improved mission life.

The fingerprints of climate warming on cereal crops phenology and adaptation options

“…Resilience to unpredictable weather will also benefit from intercropping, with the creative arrangement of multiple interacting crop species to diversify the field and the landscape 101 , 172 , 285 , 286 . Sloat et al 287 reported that warming impact on maize, wheat and rice could be moderated by migration of these crops over time and the expansion of irrigation. Multiple-cropping systems and strategies to integrate animals and crops will make more efficient use of natural resources and applied inputs; these include systems such as permaculture, agroforestry, alley cropping, intercropping and sowing C 4 crops compared to C 3 crops.…”

Automated Satellite-Based Assessment of Hurricane Impacts on Roadways

“…Moreover, their high operating costs are a burden on large-scale applications. In recent years, the dramatic drop in satellites' launching cost and the growing number of satellites in orbit significantly reduced the cost of highresolution satellite imagery [3]. Commercial satellite providers can offer high-resolution images (0.3 to 0.5 pixels/meter) with a daily and sub-daily revisiting frequency for most parts of the globe.…”

Accuracy Evaluation on Geolocation of the Chinese First Polar Microsatellite (Ice Pathfinder) Imagery

“…BNU-1 takes into account the balance between spatial resolution and revisit frequency, providing observations with finer spatial resolution than Terra/Aqua MODIS data and more revisit frequency than Landsat-8 OLI and Sentinel-2 MSI, benefiting the environmental monitoring of the polar regions. Also, the low cost of BNU-1 makes it financially feasible to construct a constellation observation system [12]. A five-satellite constellation system provides the ability to observe polar environmental elements on a daily basis with a spatial resolution finer than 100 m.…”

“…Both these models correct the errors of a satellite image by matching the CPs obtained from the target image (the image with geolocation errors) and the corresponding points from the reference image with high geolocation accuracy [17]. The parametric correction model corrects the errors by optimizing the inner and external orientation parameters in the geometric calibration model based on the differences between the CPs from the target and reference images [13,15,18], while the non-parametric model is performed by establishing the coordinates transformation model between coordinates of the target image and coordinates of the reference images based on the CPs [8,11,12].…”