Balloons remain the cheapest and most effective method for carrying large (>1,000 kg) payloads to the edge of space. The increased availability of the ULDB program provides a critical enhancement of capability for a variety of science disciplines.
VERY SMALL SPACECRAFT
Through March 2011 55 CubeSats had been launched worldwide. CubeSats are distinguished by their conformance to a size standard that allows them to be carried into orbit within a generic dispenser/carrier, the so-called P-POD. The P-POD fully encapsulates the CubeSats, providing a high level of protection for the launch vehicle and any primary payload. Owing to its simplicity and ease of adaptability to a wide variety of launch vehicles, the P-POD has been qualified for flight and utilized on a number of launch vehicles. To date, all CubeSats launched have conformed to size requirements of the standard 3-U P-POD, which accommodates up to three CubeSats measuring 10 × 10 × 10 cm.
The scientific utility of very small satellites is being demonstrated through NSF’s CubeSat-based Science Missions for Space Weather and Atmospheric Research Program. Seven scientific CubeSat missions have been competitively selected (through July 2011) from many more proposals submitted to the NSF program through its first three solicitations. The missions (FireFly, RAX, FIREBIRD, CINEMA, CSSWE, DICE, and CADRE) will pursue science goals, including studies of lightning-induced terrestrial gamma rays; electromagnetic emissions near ionospheric radar beams; mechanisms responsible for relativistic electron microbursts; energetic radiation belt electrons; electrons, ions, and neutral atoms in the ionosphere; ion-neutral coupling in the ionosphere; and the atmospheric density response in the thermosphere to extreme forcing. The NSF CubeSat program is substantially oversubscribed.
Technological gains in miniature, low-power, highly integrated electronics, microelectromechanical system devices, and other nanoscale manufacturing techniques have enabled revolutionary approaches to experimental space science that have not widely been put into practice by the heliophysics community. Small, low-cost satellites provide opportunities not typically available to traditional, large spacecraft. Low-cost “expendable” spacecraft may be deployed into regions where satellite lifetimes are constrained but where important, yet not well characterized, science linkages take place. The lower ionosphere well below 300 km and reaching down into the thermosphere at even lower altitudes is an important coupling region between the upper atmosphere and the ionosphere, yet atmospheric drag severely limits satellite lifetime against orbital decay at these altitudes. The solar chromosphere is another poorly characterized coupling region where harsh environments limit satellite lifetime. The science return per dollar to perform in situ measurements in these types of regimes, to conduct even limited lifetime measurements, is enhanced by low-cost platforms. Constellation missions, described elsewhere in this report, composed of dozens of science platforms are enabled by low-cost satellites that can be launched in large numbers from a single launch vehicle or from a number of launch vehicles as secondary or rideshare payloads at very low launch costs. Very small instrument-carrying satellites, e.g., with total mass-to-orbit in the range of 1 to 20 kg, can accommodate instruments of great utility for heliophysics. Their utility for collecting unique science measurements is greatly enhanced when they are deployed as swarms or into unique environments. Continuing technological developments will lead to even more capable spacecraft with space, weight, and power (SWAP) resources capable of supporting payload complements even more sophisticated than those permitted by the present-day 3-U CubeSats. Already, a number of organizations have developed prototype 6-U deployers and satellites that have significantly enhanced SWAP resources compared to the 3-U standard.
Launch opportunities for conforming CubeSats are becoming commonplace. The NASA Launch Services Program’s Educational Launch of Nanosatellites (ELaNa) program for educational satellites has been established and is well underway, providing launch manifesting for CubeSats. The first ELaNa CubeSats