Since Sentinels of the Heliosphere in 2008, there have been a few new missions, and a few missions have been shut down. As of Fall of 2012, here's a tour of the NASA Near-Earth Heliophysics fleet, covering the space from near-Earth orbit out to the orbit of the Moon. Revision (November 9, 2012): The RBSP mission has been renamed the Van Allen Probes. NASA Press Release.
The satellite orbits are color coded for their observing program:
Magenta: TIM (Thermosphere, Ionosphere, Mesosphere) observations
Yellow: solar observations and imagery
Cyan: Geospace and magnetosphere
Violet: Heliospheric observations
Near-Earth Fleet:
Hinode: Observes the Sun in multiple wavelengths up to x-rays. SVS page
RHESSI : Observes the Sun in x-rays and gamma-rays. SVS page
TIMED: Studies the upper layers (40-110 miles up) of the Earth's atmosphere.
FAST: Measures particles and fields in regions where aurora form.
CINDI: Measures interactions of neutral and charged particles in the ionosphere.
SORCE: Monitors solar intensity across a broad range of the electromagnetic spectrum.
AIM: Images and measures noctilucent clouds. SVS page
RBSP: (Renamed the Van Allen Probes) Designed to study the impact of space weather on Earth's radiation belts. SVS page
Geosynchronous Fleet:
SDO: Solar Dynamics Observatory keeps the Sun under continuous observation at 16 megapixel resolution.
GOES: The newest GOES satellites include a solar X-ray imager operated by NOAA.
Geospace Fleet:
Geotail: Conducts measurements of electrons and ions in the Earth's magnetotail.
Cluster: This is a group of four satellites which fly in formation to measure how particles and fields in the magnetosphere vary in space and time. SVS page
IBEX: The Interstellar Boundary Explorer measures the flux of neutral atoms from the heliopause.
Lunar Orbiting Fleet
ARTEMIS: Two of the THEMIS satellites were moved into lunar orbit to study the interaction of the Earth's magnetosphere with the Moon.
Note: A number of near-Earth missions had their orbits generated from Two-Line orbital elements valid in July 2012. Orbit perturbations since then may result in significant deviation from the actual satellite position for the time frame of this visualization.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0