#
High-Precision Orbit Propagator (HPOP)

STK Premium (Space), or STK Enterprise

You can obtain the necessary licenses for this training by contacting AGI Support at support@agi.com or 1-800-924-7244.

## Capabilities Covered

This lesson covers the following STK Capabilities:

- STK SatPro

## Problem Statement

The High-Precision Orbit Propagator (HPOP) is an orbit propagator for satellite objects. It generates ephemeris using numerical integration of the differential equations of motions. HPOP^{TM} is a trademark of Microcosm, Inc.

When you use the HPOP propagator, you can choose from several numerical integration techniques and formulations of the equations of motion. You can also include force modeling effects such as a full gravitational field model (based upon spherical harmonics), third-body gravity, atmospheric drag, and solar radiation pressure.

Because of the many parameter settings that HPOP offers, you can specify a precise model of the force model environment of almost any satellite and generate a highly accurate orbit ephemeris. HPOP can model circular, elliptical, parabolic, and hyperbolic orbits around any central body and at any distance above it.

HPOP ephemeris generation takes much more computational effort than analytical propagation.

## How to use HPOP

On the Orbit properties page of the satellite object, select **HPOP** from the Propagator menu.

If HPOP is unavailable in the Propagator menu, then you do not have a valid license for HPOP installed. Refer to the licensing topic to learn about licensing for STK and its capabilties. Or, contact AGI Technical Support.

Once you have selected HPOP as the propagator, the Orbit page will transform so that it comprises the HPOP parameters. Take the following steps to configure an HPOP satellite:

- Get a new initial vector with the Initial State Tool (optional).
- Set the satellite's interval and step size.
- Choose a coordinate system.
- Choose a coordinate type and enter values for the orbital parameters.
- Select and customize the force models that you want to apply to the trajectory computations.
- Select and customize the integration method that you want to use to compute the trajectory.
- Define a covariance error matrix (optional).

To review computational specifications, refer to the HPOP technical Notes topic.