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upon and bore-sighted with the microwave radiometer described in the accompanying article. Both instruments therefore executed the same scan pattern caused by the combined effects of the probe motion and a rotation of the radiometers in a plane normal to the probe-sun line. It was originally E. J. Smith

Both Phase 1 of the Square Kilometre Array (SKA1) and the full SKA have the potential to dramatically increase the science return from future astrophysics, heliophysics, and especially planetary missions, primarily due to the greater sensitivity (A EFF / T SYS ) compared with existing or planned spacecraft tracking facilities. While this is not traditional radio astronomy, it is an opportunity for productive synergy between the large investment in the SKA and the even larger investments in space missions to maximize the total scientific value returned to society. Specific applications include short-term increases in downlink data rate during critical mission phases or spacecraft emergencies, enabling new mission concepts based on small probes with low power and small antennas, high precision angular tracking via VLBI phase referencing using in-beam calibrators, and greater range and signal/noise ratio for bi-static planetary radar observations. Future use of higher frequencies (e.g., 32 GHz and optical) for spacecraft communications will not eliminate the need for high sensitivities at lower frequencies. Many atmospheric probes and any spacecraft using low gain antennas require frequencies below a few GHz. The SKA1 baseline design covers VHF/UHF frequencies appropriate for some planetary atmospheric probes (band 1) as well as the standard 2.3 GHz deep space downlink frequency allocation (band 3). SKA1-MID also covers the most widely used deep space downlink allocation at 8.4 GHz (band 5). Even a 50% deployment of SKA1-MID will still result in a factor of several increase in sensitivity compared to the current 70-m Deep Space Network tracking antennas, along with an advantageous geographic location. The assumptions of a 10X increase in sensitivity and 20X increase in angular resolution for SKA result in a truly unique and spectacular future spacecraft tracking capability.Advancing Astrophysics with the Square Kilometre Array

Interplanetary CubeSats could enable small, low-cost missions beyond low Earth orbit.This class is defined by mass <~ 10 kg, cost < $30 M, and durations up to 5 years. Over the coming decade, a stretch of each of six distinct technology areas, creating one overarching architecture, could enable comparatively low-cost Solar System exploration missions with capabilities far beyond those demonstrated in small satellites to date. The six technology areas are: 1) CubeSat electronics and subsystems extended to operate in the interplanetary environment, especially radiation and duration of operation; 2) Optical telecommunications to enable very small, low-power uplink/downlink over interplanetary distances; 3) Solar sail propulsion to enable high ΔV maneuvering using no propellant; 4) Navigation of the Interplanetary Superhighway to enable multiple destinations over reasonable mission durations using achievable ΔV; 5) Small, highly capable instrumentation enabling acquisition of high-quality scientific and exploration information; and 6) Onboard storage and processing of raw instrument data and navigation information to enable maximum utility of uplink and downlink telecom capacity, and minimal operations staffing. The NASA Innovative Advanced Concepts (NIAC) program in 2011 selected Interplanetary CubeSats for further investigation, some results of which are reported here for Phase 1.