International sun-Earth explorer: a three-spacecraft program

The Lunar Environment Heliophysics X-ray Imager (LEXI) Mission

The Lunar Environment heliospheric X-ray Imager (LEXI) is a wide field-of-view soft X-ray telescope developed to study solar wind-magnetosphere coupling. LEXI is part of the Blue Ghost 1 mission comprised of 10 payloads to be deployed on the lunar surface. LEXI monitors the dayside magnetopause position and shape as a function of time by observing soft X-rays (0.1-2 keV) emitted from solar wind charge-exchange between exospheric neutrals and high charge-state solar wind plasma in the dayside magnetosheath. Measurements of the shape and position of the magnetopause are used to test temporal models of meso- and macro-scale magnetic reconnection. To image the boundary, LEXI employs lobster-eye optics to focus X-rays to a microchannel plate detector with a 9.1× ∘ 9.1 ∘ field of view.

Soft X-ray and ENA Imaging of the Earth's Dayside Magnetosphere

The LEXI and SMILE missions will provide soft X-ray images of the Earth's magnetosheath and cusps after their anticipated launch in 2023 and 2024, respectively. The IBEX mission showed the potential of an Energetic Neutral Atom (ENA) instrument to image dayside magnetosheath and cusps, albeit over the long hours required to raster an image with a single pixel imager. Thus, it is timely to discuss the two imaging techniques and relevant science topics. We simulate soft X-ray and low-ENA images that might be observed by a virtual spacecraft during two interesting solar wind scenarios: a southward turning of the interplanetary magnetic field and a sudden enhancement of the solar wind dynamic pressure. We employ the OpenGGCM global magnetohydrodynamics model and a simple exospheric neutral density model for these calculations. Both the magnetosheath and the cusps generate strong soft X-rays and ENA signals that can be used to extract the locations and motions of the bow shock and magnetopause. Magnetopause erosion corresponds closely to the enhancement of dayside reconnection rate obtained from the OpenGGCM model, indicating that images can be used to understand global-scale magnetopause reconnection. When dayside imagers are installed with high-ENA inner-magnetosphere and FUV/UV aurora imagers, we can trace the solar wind energy flow from the bow shock to the magnetosphere and then to the ionosphere in a self-standing manner without relying upon other observatories. Soft X-ray and/or ENA imagers can also unveil the dayside exosphere density structure and its response to space weather.

Recent gravity-assist trajectories for interplanetary and solar exploration

This paper describes how lunar and planetary gravity assists have been used to design trajectories that have enabled challenging missions, currently flying or in development, at the Applied Physics Laboratory (APL) of Johns Hopkins University, to explore the Sun, and the planets closest to and farthest from it. This is a continuation of a paper presented at the first New Trends in Astrodynamics and Applications conference, January 2003. That paper concentrated on the Third International Sun-Earth Explorer (ISEE-3) halo orbit mission, later known as the International Cometary Explorer, or ICE, and the Near Earth Asteroid Rendezvous (NEAR) mission of APL, and the ground-breaking orbits that those spacecraft used to accomplish their ambitious goals. This paper gives much more information about current APL missions, MESSENGER, STEREO, and New Horizons, which were only briefly described in the previous paper.

Background and applications of astrodynamics for space missions of the johns hopkins applied physics laboratory

This paper describes astrodynamic techniques applied to develop special orbital designs for past and future space missions of the Applied Physics Laboratory (APL) of Johns Hopkins University, and background about those techniques. The paper does not describe the long history of low Earth-orbiting missions at APL, but rather concentrates on the astrodynamically more interesting high-altitude and interplanetary missions that APL has undertaken in recent years. The authors developed many of their techniques in preparation for, and during, the Third International Sun-Earth Explorer (ISEE-3) halo orbit mission while they worked for the Goddard Space Flight Center (GSFC) of NASA during the 1970s and 1980s. Later missions owed much to the ground breaking work of the trajectory designs for ISEE-3 (later known as the International Cometary Explorer, or ICE). This experience, and other new ideas, were applied to the APL near Earth asteroid rendezvous (NEAR) and comet nucleus tour (CONTOUR) discovery missions, as well as to APL's future MESSENGER, STEREO, and New Horizons missions. These will be described in the paper.