## jat.core.cm.DE405Plus

#### Introduction

The DE405Plus class provides a DE405 Ephemeris reader for the sun, planet, and moon positions and velocities. The user can choose between a common set of reference frames.

The class also provides a force acceleration function for propagation of trajectories. The force contribution from the sun, each planet individually, and the moon can be turned on or off.

#### Reference Frames

 Acronym Name Origin X-axis Y-axis X-Y-Plane Z-axis J2000 Sun Mean Equinox at 12:00 Terrestrial Time on 1 January 2000 Earth's spin axis or celestial North Pole. ICRF International Celestial Reference Frame Sun origin of right ascension north celestial pole HEE Heliocentric Earth Ecliptic Sun Sun to Earth line Ecliptic GCRF Geocentric Celestial Reference Frame Earth ECEF Earth-Centered Earth-Fixed Earth center of mass 0° latitude (Equator) and 0° longitude (Greenwich) Earth's equatorial plane ECI Earth-Centered Inertial Earth vernal equinox Earth's equatorial plane

References:

http://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/icrs-narrative

http://en.wikipedia.org/wiki/Earth-centered_inertial

#### Examples

The example below shows a trajectory that was progated in the ICRF frame for 300 days. The initial conditions were

$$\mathbf{r_0}=2e8, 0, 0 km$$

$$\mathbf{v_0}= 0, 24.2, 0 km/s$$

In one case, only the sun was turned on, in the other case, Jupiter was turned on additionally. After 300 days, the position of the spacecraft shows a difference of about 150,000 km, depending on whether Jupiter was taken into account or not.