PLANETARY SCIENCE WITH BALLOON-BORNE TELESCOPES: A SUMMARY OF THE BOPPS MISSION AND THE PLANETARY SCIENCE THAT MAY BE POSSIBLE LOOKING FORWARD

摘要

The National Aeronautics and Space Administration (NASA) and the planetary science community have recently been exploring the potential contributions of stratospheric balloons to the planetary science field. A study that was recently concluded explored the roughly 200 or so science questions raised in the Planetary Decadal Survey report and found that about 45 of those questions are suited to stratospheric balloon based observations. In September of 2014, a stratospheric balloon mission called BOPPS (which stands for Balloon Observation Platform for Planetary Science) was flown out of Fort Sumner, New Mexico. The mission had two main objectives, first, to observe a number of planetary targets including one or more Oort cloud comets and second, to demonstrate the applicability and performance of the platform, instruments, and subsystems for making scientific measurements in support of planetary science objectives. BOPPS carried two science instruments, BIRC and UWis. BIRC is a cryogenic infrared multispectral imager which can image in the 0.6-5 μm range using an HgCdTe detector. Narrow band filters were used to allow detection of water and CO_2 emission features of the observed targets. The UWis is an imager with the science range of 300 to 600 nm. A main feature of the UWis instrument is the incorporation of a guide camera and a Fine-Steering Mirror (FSM) system to reduce image jitter to less than 100 milliarcsecond. The BIRC instrument was used to image targets including Oort cloud comets Siding Spring and Jacques, and the dwarf planet 1 Ceres. BOPPS achieved the first ever earth based CO_2 observation of a comet and the first images of water and CO_2 of an Oort cloud comet (Jacques). It also made the first ever measurement of 1 Ceres at 2.73 μm to refine the shape of the infrared water absorption feature on that body. The UWis instrument, mounted on its own optics bench, demonstrated the capability for image correction both from atmospheric disturbances as well as some of the residual motion from the gondola that was not addressed by the gondola's coarse pointing systems. The mission met its primary science and engineering objectives. The results of the BOPPS mission will feed into the body of science knowledge, but also feed into future planning for more science from balloon-borne platforms. A notional platform called Gondola for High-Altitude Planetary Science (GHAPS) has been explored, and this concept platform can address a number of important decadal questions. This paper provides a summary of the assessment of potential balloon borne observations for planetary science purposes including where potential science contributions can be expected, the necessary performance/characteristics of the platform, and other features required or desired. The BOPPS mission is summarized including descriptions of the main elements and key science and engineering results. The paper then briefly describes GHAPS, and the salient features that can make it a valuable tool for future planetary observations.