Since the local interstellar medium and the heliosphere it surrounds are three dimensional, it seems to me launching four or more identical probes in different directions from the Solar System with particle and field instruments, plasma and dust detectors as well as radio science instruments would be the way to go. Using a solar sail and a gravity assist from Jupiter plus adding an extra booster rocket to the launch vehicle to speed them along into the interstellar medium at at least double the velocity of Voyager 1 would be in reach if technology available now or in the near future. To simply and lighten them, spin stabilization could be used to keep the probes antenna pointed at Earth while the instruments can scan in all directions. As for power, I imagine using RTG's based on Americium 241 and a Stirling engine would ensure enough power to operate the spacecraft for well beyond 1,000 A.U and fifty years of mission operations. Efficiency of the RTG's used by Voyager has a seven percent efficiency rating while improved RTG's have increased it to thirty percent.
Since the local interstellar medium and the heliosphere it surrounds are three dimensional, it seems to me launching four or more identical probes in different directions from the Solar System with particle and field instruments, plasma and dust detectors as well as radio science instruments would be the way to go. Using a solar sail and a gravity assist from Jupiter plus adding an extra booster rocket to the launch vehicle to speed them along into the interstellar medium at at least double the velocity of Voyager 1 would be in reach if technology available now or in the near future. To simply and lighten them, spin stabilization could be used to keep the probes antenna pointed at Earth while the instruments can scan in all directions. As for power, I imagine using RTG's based on Americium 241 and a Stirling engine would ensure enough power to operate the spacecraft for well beyond 1,000 A.U and fifty years of mission operations. Efficiency of the RTG's used by Voyager has a seven percent efficiency rating while improved RTG's have increased it to thirty percent.