GJB 2502.3-2015 Test Methods for Thermal Control Coatings of Spacecraft Part 3: Emissivity Test

scope
This section specifies the purpose, scope, accuracy, principles, equipment and requirements, conditions, samples, procedures, data processing, and reporting requirements for testing the hemispherical emissivity and normal emissivity of spacecraft thermal control coatings.
This section is applicable for testing the emissivity of thermal control coatings on spacecraft.

Hemisphere emissivity steady-state calorimeter method (Method 2011)
Test purpose
Measure the hemispherical emissivity of the spacecraft thermal control coating test sample and reference sample.

Normal emissivity method (Method 2021)
Test purpose
Measure the normal emissivity of the spacecraft thermal control coating test sample.

Radiometer method (Method 2031)
Test purpose
Measure the hemispherical emissivity of the spacecraft thermal control coating test sample.
Testing scope and accuracy
The range of hemispherical emissivity testing is 0.03~0.95, with a testing accuracy of 0.015.
Test Principle
The output signal of the radiometer detector is linearly related to the emissivity of the tested sample. By comparing the high and low emissivity reference samples equipped with the radiometer with the output signal of the tested sample, the emissivity of the tested sample can be directly obtained.
Testing equipment and requirements
Radiometer detector: repeatability ± 0.01.
Millivolt meter: Sensitivity 0.01mV.
Heat sink: Good thermal conductivity and high surface radiation.
Reference sample: required to comply with the provisions of 4.3 in GJB 2502.1-2015.
test conditions
The temperature of the tested sample should be the same as that of the reference sample.
The laboratory temperature is between 15 ° C and 25 ° C, and other conditions shall comply with the provisions of section 4.1 of GJB 2502.1-2015.
Tested sample
The surface should be flat, with good thermal conductivity and no pollution.
The size should be larger than the diameter of the detector, and the thickness should generally not exceed 2mm.
The curvature radius should meet the requirements of the instrument.
Other requirements shall comply with the provisions of 4.3 in GJB 2502.1-2015.
test program
Pre-test preparation
Preheat the instrument for about 30 minutes.
test
Place the high and low emissivity reference samples on the heat sink, and place the detectors on the high and low emissivity reference samples respectively. By fine-tuning, make the values displayed on the counting instrument equal to their respective emissivity values. Repeat this step.
Place the test sample on a heat sink, place the detector on the surface of the test sample for about 90 seconds, and wait for the reading to stabilize. This reading is the emissivity of the test sample. This process should be carried out at least three times.
data processing
Take the arithmetic mean of three test values as the hemispherical emissivity of the tested sample.
Test Report
The requirements for the test report shall comply with the provisions of 4.4.3 in GJB 2502.1-2015.

Reflex Method - Portable (Method 2041)
Test purpose
Measure the hemispherical emissivity of thermal control coatings on spacecraft and component surfaces.


Radiometer emissivity tester D&S AERD