505.7-1 INTRODUCTION
This Annex describes methods of simulation designed to examine the effects of solar radiation on materiel. The main quantities to be simulated are the spectral energy distribution of the sun as observed at the Earth's surface and the intensity of received energy, in combination with controlled temperature conditions. However, it may be necessary to consider a combination of solar radiation - including sky radiation - with other environments, e.g., humidity, air velocity, etc.
1.1 Purpose
This method has two purposes:
- a. To determine the heating effects of solar radiation on materiel.
- b. To help identify the actinic (photo degradation) effects of exposure to solar radiation.
1.2 Application
Use this method to evaluate materiel likely to be exposed to solar radiation during its life cycle in the open in hot climates, and when heating or actinic effects are of concern. This Method is valuable in evaluating the effects of direct exposure to sunlight (solar spectrum and energy levels at sea level). Procedure I is useful in determining the temperature increase (over ambient) of materiel caused by solar loading. Although not intended for such, Procedure II may be used to simulate the ultraviolet effect of solar radiation at different locations and altitudes by using various radiation sources that allow reasonable comparison to measurements of these natural solar radiation conditions.
In addition to using Procedure I to evaluate the effects of direct sunlight (actinic effects as well as directional and non-uniform heating for exposed materiel), use Procedure I for determining the heating effects (response temperature) for materiel enclosed within an outer container.
Use Procedure II to evaluate the actinic effects on materiel exposed to long periods of sunshine. The spectrum of the solar array must be measured and conform to the spectrum identified in Table 505.7-I. Deviations from this table may be justified if the test requirements are based on the tailoring process, or if a specific frequency band is of concern. Detail and justify any deviation.
1.3 Limitations
- a. This test Method does not consider all of the effects related to the natural environment (see Annex A, paragraph 7.2) and, therefore, it is preferable to test materiel at appropriate natural sites.
- b. If the installed environment for an item is within an enclosure, the enclosure must be provided in order to characterize the environment and properly address the heating effects. Once the enclosed environment has been characterized, further testing could be done using Method 501.7.
- c. This Method is not intended to be used for space applications due to the change in irradiance.