## 3 Adaptation of COTS for space applications  
As described in the section above, both the functionality and integration of magnetic sensing technologies are continuously evolving. Moreover, as electronic devices and sensors are becoming essential parts of our daily lives and as users test them exhaustively the technology undergoes a continuous on-ground qualification process by which reliability is increased tremendously. By the NASA nomenclature [52, 53] of TRL - Technology Readiness Level - a systematic metric / measurement system that supports assessments of the maturity of a particular technology and the consistent comparisons of maturity between different types of technologies, and considering that a relevant environments is not restricted to the space environment, the TRL of a device that has been on the market for one year can be considered TRL 6 or 7: a demonstration in a relevant environment has been performed. Regarding magnetic sensing technologies, fluxgate, AMR and Hall effect vector sensors, and proton, helium or cesium scalar magnetometers can be considered mature sensors. The GMR, MI and SDT sensors described above, can be considered to be at a lower maturity stage. Besides, fluxgate sensors and several scalar sensors have been widely used for flight achieving in their missions a TRL 9. The key question is how to increase the maturity level of the alternative COTS sensors. Keeping in mind the philosophy behind modern satellite design and the resources restrictions of some projects, very small sensors with a medium-to-high maturity level can be considered good candidates for space, the jump to space being achieved when it is demonstrated that the sensors can withstand the conditions in space for the life of the mission. The space environment, with extreme vacuum, temperature and radiation conditions, is highly hostile compared to that on the surface of the Earth. Besides, the satellites are exposed to strong mechanical stresses during the launch. Sensors to be used in flight need to be tested under these conditions. The upscreening for space qualification is a long and difficult process for magnetic sensors. Though the upscreening is usually conceived for each particular mission, in general terms the procedure consists of a sequence of thermal, vacuum, live cycle and radiation tests devoted to check the integrity of the sensors. Most of the commercial components have a plastic package. Some plastics can outgas, thereby staining optical surfaces, depositing wherever and possibly causing serious damages. To avoid this, it is essential to define an outgasing test for the COTS with plastic package susceptible to outgas, before they fly. Fluxgates for flight usually have ceramic military packages, though there are some with plastic packages too. But the truth is that many components with plastic package do not outgas. For instance, some tests have been developed for AMR sensors of the HMC series by Honeywell showing that they do not present outgasing [54]. But the vacuum can also cause other damages like cracks in the components if for example bubbles were formed during the manufacture. The temperature is another issue that needs to be taken into account. Temperature in the solar system ranges from temperatures as high as 485 \({}^{\circ}\)C on Venus, due to the greenhouse effect produced by its dense atmosphere of carbon dioxide, to -200 \({}^{\circ}\)C for the outer planets, with intermediate temperatures as high as 400 \({}^{\circ}\)C in Mercury, and as low as -130 \({}^{\circ}\)C in Mars and Jupiter or -190 \({}^{\circ}\)C in Saturn. For satellites orbiting around the Earth the temperatures are not that extreme, but they can be far outside the commercial temperature range (0\({}^{\circ}\)C, 70 \({}^{\circ}\)C) and even the industrial range (-40\({}^{\circ}\)C, 85 \({}^{\circ}\)C).