Vibration tests on the first Slovenian satellites, Nemo HD and Trisat

There is a lot of talk currently about the launch of the first Slovenian satellites, Nemo HD and Trisat, into space. We are proud to announce that a part has been played in this by Domel and VTN (Vibroakustična testiranja NELA). In recent years we have carried out vibration tests for both projects on shakers, the latest test being conducted for Trisat just recently at the end of April 2020. The main purpose of the tests was to assess the robustness of the bearing structure and installed satellite components during the lift-off procedure of the Vega rocket vehicle of the company Arianespace.

The satellites will be launched as part of an ESA (European Space Agency) project which will involve the launching of 53 micro and nanosatellites from 13 countries. Nemo HD is classed as a microsatellite (this launch will involve 7 such satellites), weighing 65 kg, which will peel off at 515 km into a sun-synchronous orbit. Trisat is classed as a nanosatellite, weighing barely 4 kg (and measuring 10x10x30 cm), and will be deployed at around 530 km.

The Nemo HD microsatellite will be in orbit for five years. It is a prototype microsatellite for high-precision interactive remote sensing, which will allow it to capture multispectral images of Earth’s surface and record high-resolution videos in real time. We can use it to observe the state of vegetation, water and urban settlements for applications that include agriculture, forestry, urban planning, ecology and energy. The purpose of the satellite is a technological demonstration. [1]

The four-kilo nanosatellite Trisat will orbit the Earth for an anticipated six years. First and foremost it is intended for testing new space electronics. On-board the satellite there will also be a miniature hyperspectral or multispectral camera, operating in the short wave infrared (SWIR) field, which will capture images of the Earth’s surface every day. These images can be used to monitor precisely the pollution of water, vegetation moisture levels, to identify fire flashpoints and detect volcanic dust in the upper layers of the atmosphere for the needs of the aviation industry. [1]

The actual lift-off and deployment are relatively quick, with the rocket vehicle reaching an altitude of 100 km in 3 minutes. The test procedures are therefore appropriately adapted to this. Arianespace has prescribed precise vibration profiles for its SSMS (Small Spacecraft Mission Service) on the Vega rocket. The testing comprises very short tests lasting a total of less than 11 minutes. In terms of frequency the stimulation is carried out in the range from 5 Hz to 2000 Hz. The greatest amplitude of acceleration is 2.5 G. In the pulse test, in sinus form at 13 Hz we have an amplitude of 10 G in a duration of 1s. [2], [3] 

Figure 1:  Demonstration bearing structure of the Nemo HD satellite on a sliding table during vibration testing

Figure 1:  Demonstration bearing structure of the Nemo HD satellite on a sliding table during vibration testing

Figure 2:  Range of random vibrations (duration ~ 2 minutes)

Figure 2:  Range of random vibrations (duration ~ 2 minutes)

Based on the activities carried out, the analysis of carrying functions and improvements to the bearing structures, we can expect both satellites to withstand the rocket launch. The profile of the vibration test is in itself not extremely demanding, and is much gentler than the tests we perform in developing products for the automobile industry (e.g. engines 484, stepper motors 701 and so forth). But in this case the vital part of the testing is to check the structures – satellites attached to the Vega rocket cannot afford to have any parts fall off, since this can damage other satellites or the rocket itself, which can be very costly.

Figure 3:  Vibration test of the ATTM Skylabs module on the bearing structure of the Trisat satellite

Figure 3:  Vibration test of the ATTM Skylabs module on the bearing structure of the Trisat satellite

Figure 4:  Trisat nanosatellite

Figure 4:  Trisat nanosatellite [3]

The satellites will orbit the Earth approximately every 95 minutes and will communicate with the Earth station. Trisat will be above the area of Slovenia every day at around 11 am.  Additional information on the project, its possibilities and wider significance can be found on the links below.

Jure Pfajfar

Access to video - "Vega lifts off":