The option to generate orbits around Jupiter is available only for Advanced users.

Overview

For Jupiter, the SPENVIS orbit generator can be used to compute general (elliptical) orbits around the planet and flybys. It takes into account the oblateness of Jupiter, the gravitational attraction of Sun and the four Galilean moons and the solar radiation pressure.

The spacecraft trajectory is defined in terms of a mission, i.e. in addition to defining the spacecraft orbital elements, the time period the spacecraft is in orbit has to be specified as well. In the case of Jupiter, by default, only one segment can be considered.

Once the mission has been defined, orbital parameters have to be specified. Once this is done, a page with a summary table of the mission segment is presented and the trajectory generation can be started.

Mission definition

A mission is defined by the time of the end of the mission (the start of the mission is set to the starting point of the orbit for the segment). The mission end can be specified by the total mission duration or by an end date.

The start time of the mission segment is set to the start time of the orbit defined for the segment.

The segment and mission lengths and epochs defined in this fashion are used by the environment and effects models that run on a spacecraft trajectory. Hence, these parameters need not be specified when running the models in question. In particular, the radiation sources and effects models use the segment and mission lengths to scale orbit averaged fluxes to segment and mission fluences, or to add dose contributions from trapped particles to those from solar protons (which are defined for the total mission length only).

Trajectory uploads

Advanced users have also the option to upload a trajectory file.

Solar radiation pressure

The user has the option to input parameters for Solar radiation pressure. The Solar radiation pressure parameter is defined as  0.451x10^-8 K A/M, where:

• K is the material parameter:
  

  K = 1 - gamma + rho	plate
  K = 1 - gamma	sphere
  K = 2	plate with perfect specular reflection
  K = 1	sphere with perfect specular reflection or perfect absorption
  K = 1.44	sphere with perfect diffuse reflection

  rho and gamma are the reflectivity and transmittivity of the satellite.
• A is the total reflective area (m²) of satellites and plates; for spherical satellites it is the cross sectional area.
• M (kg) is the mass of the satellite.

Orbital parameters

A spececraft orbit is described by means of a number of parameters, a start date and a duration. The start date corresponds to the date and time of the first point written on the output file. The duration can be specified as a number or orbits, or directly as a duration in days (non-integer numbers of orbits or days are allowed). It is not expedient to generate a trajectory file for the whole of a typical mission duration, instead a duration should be selected that guarantees coverage of all planetographic locations. For very high altitude trajectories, a short duration is sufficient, as the models that can be run on a trajectory do not depend on spacecraft location outside the magnetosphere.

It is recommended to produce graphical representations of the trajectory before proceeding with the environment models.

Two different orbit types are available:

• general (elliptical) orbit;
• hyperbolic (flyby) orbit.

and all parameters have to be entered. The segment title is used for annotating the report and output files.

General orbit parameters

Altitude

The orbit altitude can be specified in three ways, by specifying the following sets of parameters:

1. the altitude of the perijove and apojove of the trajectory, respectively, above the mean radius of Jupiter;
2. the length of the semi-major axis and the eccentricity.

Note that for general (elliptical) orbits the semi-major axis is positive and the eccentricity must be greater or equal (circular orbit) to zero and less than one.

Inclination

The orbit inclination is the angle between the orbital plane and the equatorial plane, measured at the ascending node in the direction of orbital motion. The orbit is called direct when the inclination is smaller than 90° and retrograde when the inclination is larger than 90°.

Right ascension of the ascending node

The right ascension of the ascending node is the angle in the equatorial plane between the line of nodes and the direction to the vernal equinox, measured from the vernal equinox (the direction of the intersection of the ecliptic and equatorial planes) towards the ascending node. Alternatively, the longitude of perijove or apogee can be specified.

Argument of perijove

The argument of perijove is the angle measured in the orbital plane from the ascending node to the perijove.

True anomaly

The true anomaly is the angle from the perijove direction to the satellite direction.

Hyperbolic orbit parameters

The orbit altitude can be specified by providing the length of the semi-major axis and the eccentricity. Note that for hyperbolic orbits the semi-major axis has a negative value and the eccentricity must be greater than one.

The remaining orbital elements (inclination, right ascension of the ascending note, argument of perijove and true anomaly) are defined in the same way as in the general orbit case.

Advanced users have the option to set the output resolution of the orbit generator. Up to three time steps (s) can be set for three different regions defined by a limiting altitude (km).

Mission summary

When the mission segment has been defined, the mission summary page is presented. This page provides a table with the orbit type and duration (or number of orbits) and the start and end time for the mission segment. This table can be used for a final check of the mission definition. The orbit generator will check the segment definitions for inconsistencies. If any discrepancies are found, an error message will be displayed.

Pressing the button will start the calculation and bring up the "Results" page.

The button calls up the model selection page for consecutive runs of multiple models. This feature is available for advanced users only.
Warning: using these buttons deletes all existing output from the orbit generator and from any model that uses this output, in order to ensure consistency in the outputs.