Nowadays the qualification of only one component following ESA or NASA Standards implies an investment beginning from 1 million dollar and a certification time of around two years.
Space shuttle (1981) IBM CPU – AP-101 (Source: NASA)
The gained experience of the last sixty years in many space missions and with different technologies allowed institutions like ESA and NASA to develop qualification guidelines and standards, which are manuals to be followed and used for the qualification of electronic parts for space missions. The standards defined by the ESA can be found in the European Space Components Information Exchange System (ESCIES) website (https://escies.org/webdocument/showArticle?id=167). A database of qualified electronic components including their test reports is also available on the ESCIES Website. (https://escies.org/labreport/radiationList).
The validation and qualification process consists in the preparation of the hardware and the devices (Device Under Test or DUT) to be tested, the execution of the test itself and the evaluation of the results, which will be published in a test report.
Depending on the mission, few components will be screened during the test or it will be necessary to analize the entire component batch in order to achieve the qualification of the whole system. It means, in some cases few parts are enough to guarantee the qualification of the system (e.g. radiation tests) and in other cases the complete batch (outgassing) has to be tested. During the tests the relevant parameters of the devices will be characterized under space conditions. One important point for a successful qualification is to guarantee that the tested components were produced with a similar manufacturing process; in other words all the qualified parts are identical (geometry, size, materials, etc.), and consequently they belong to the same batch.
After the qualification a test report and a datasheet will be generated containing the parameter values and limits relevant for the use of the electronic parts in space.
A full qualification of a component is very laborious. It takes few years and requests a high financial investment. A full qualification is called “Screening Test”. In the screening test following tests have to be performed:
- Electrical test
- Seal test
- Visual inspection
- Mechanical shocks
- Vibration test
- Constant acceleration
- Thermal test
- Radiation test
- High Temperature Stabilization Bake
- Temperature cycling
- Thermal Shock
Following the ESA Standards described in the document “ECSS-Q-ST-60-13C_Space product assurance”, tree different classes have been defined. The difference between the classes depends of the deepness of the qualification process. In summary the Class 1 represents a full qualification and the Class 3 a light qualification, mainly radiation testing.
To become an idea how a qualification test is a short description of the Total Ionizing Dose (TID) test follows below:
Preparation of the DUT test boards. Here two configurations (Bias Condition) are important. One is the “Off-Mode” where all the pins are connected to ground. The second one is the “On-Mode” where the device is configured in a specific operating state but it will be kept without function, like in “Stand-by” mode. It means no signal will be processed during the test. This two test configurations will be used for the irradiation of the DUTs. A Cobalt-60 will be used as radiation source. During the irradiation, the DUTs will be characterized in time intervals with a tester (Automatic Test Equipment – ATE). The characterization results will show the degradation of the devices during the test. The degradation depends on the accumulated radiation dose. For example, the power consumption will increase the higher the radiation dose.
Upon completion of the test, it is possible to observe the variation of some electrical parameters and in some cases by a specific radiation dose the destruction of the device.
BIAS Condition TID Test for the LTC2052
OPAMP power supply degradation
OVERQUALIFICATION? ARE COTS ROBUST ENOUGH?
ITAR components comply with very severe requirements and offer a high reliability for their usage in extreme environments. An ITAR component can have a radiation tolerance of 300 krad. During a LEO mission, a total dose of 1 krad will be accumulated in one year . In this case the use of ITAR components does not match the mission requirements. It is valid to say that the ITAR components are over-qualified for LEO missions.
Stand of DUTs ready for the irradiation
Furthermore, the ITAR problematic is bound with export restrictions. The export licensing process takes around six months and there is no guarantee to get the permission. This is a major problem for small and medium-sized enterprises (SMEs) also American SMEs and retards their business process. Another disadvantage is that the ITAR EEE parts are based on a robust but also old technology, and do not reach the newest High-Tech electrical and functional levels. Another important point is the price of ITAR components, which is very high and a financial obstacle for SMEs that want to enter in the space field and are not in possession of major capital resources.
The new space era begins with the born of the Picosatellites. In February 2000 the Stanford University launched the microsatellite OPAL. This satellite was the mothership of six Picosatellites, which demonstrated the feasibility of new space platforms for research experiments . Since the beginning of the century such new space platforms has been used by many universities, research institutes and space companies for research, technology demonstration, technology validation and commercial services. In order to keep costs low, Commercial-Of-The-Shelf (COTS) components have being used. These components support the missions for a limited period, however reborn the usage of COTS components in space.
Nowadays many institutions continue developing and launching nanosatellites based on COTS. The installed components will be in very rare mission qualified or even the use of very few ITAR components happened. Most of these missions never qualify the electronic components and trust in the performed simulations and to luck. In the best case the developing teams do test the electronics but in a module level or a board level. During this process, the electronic board will be irradiated with gamma rays and will be tested with a test software until errors appear or in case nothing happen the test will be considered as passed. This solution is often practiced however; it is not the professional way to develop space electronics. The standard procedure from the ESA and NASA testing each component is the recommended way to design electronics for space, especially because is necessary to understand the behaviour of all components under such conditions. In conclusion, each component of the system should be tested in order to comply with the mission requirements, and the components must be selected before the mission design begins. The uncertainty of not knowing for how long the electronics will properly work in space will never permit the professional development of small satellites, what is a necessity for high quality commercial services and products.