Help: Illumination model

Table of Contents	ECSS	Model Page
Background Information	Miscellaneous models
	Illumination model

Overview

This tool evaluates the irradiation incident on an oriented surface of a spacecraft over the spacecraft trajectory. SPENVIS verifies if a spacecraft trajectory has been generated prior to accessing the model page. If not, an error message is displayed with a link to the orbit generator. Please note that running the orbit generator will delete all existing output resulting from models that use the spacecraft trajectory.

The input parameters and options for the models are described below. When the input form has been completed, pressing the button will start the calculation and bring up the "Results" page.

Model parameters

Two sets of parameters have to be defined: one for the definition of the radiation sources, and one for the orientation of the exposed surface.

Illumination parameters

The following parameters are needed to define the irradiation sources:

the solar constant for the evaluation of the direct solar flux;
the temperatures at the sub-solar point and at the night side for the Earth emitted infrared radiation;
the Earth albedo for the Earth reflected radiation;

Orientation of the exposed surface

The orientation of the exposed surface is defined in the reference frame attached to the satellite. The reference frame is defined when the spacecraft orbit is generated.

The direction of the normal of the exposed surface can be defined as being parallel to the polar axis of the satellite reference frame, or the spherical coordinates of the surface normal can be specified (see Fig. 1).

Figure 1. Definition of the polar and azimuthal angle with respect to the local coordinate system.

Results

The illumination tool produces the files listed in the table below. A description of the file formats can be brought up by clicking on their description in the table.

The report file spenvis_ilp.html contains the input parameters and summary tables. The spenvis_ilo.txt file contains incident power and orientation angles for each orbital point.

**Output files generated by the illumination tool**
File name	Description
`spenvis_ilp.html`	Report file
`spenvis_ilo.txt`	Incident power and orientation angles for each orbital point

To generate plots, select the plot type(s), options and graphics format, and click the or button. The current page will be updated with the newly generated plot files.

Last update: Mon, 12 Mar 2018