At NASA’s Jet Propulsion Laboratory in Southern California, engineers are testing the SkyFall Earth‑observation mission’s antennas inside an electromagnetically shielded, low‑reflection chamber. The goal is to precisely measure transmit and receive behavior and to rule out interference — a prerequisite for reliable data from ground‑penetrating radar sensors.
Why the tests are crucial
Before an instrument goes to orbit, its antenna must demonstrate that it can transmit and receive signals with the intended directionality, sensitivity and polarization. Accuracy is especially important for ground‑penetrating radar: errors in antenna characteristics can distort backscatter profiles and thus compromise analyses of ice, permafrost or groundwater — with direct consequences for climate modelling and forecasting.
How measurements are taken
The antenna is placed inside an absorber‑lined chamber whose walls dampen stray signals and minimize reflections. During measurements the antenna points upward to reduce interactions with the floor and multipath effects. Coaxial cables connect the test equipment and the antenna — these connections are also inspected, since contact issues or insufficient shielding can introduce spurious signals.
Key performance metrics
Engineers record the radiation pattern, antenna gain and polarization across the relevant frequency band. Ground‑penetrating radars typically use lower frequencies so the waves penetrate deeper into ice and soil layers. From the measurements it is possible to determine how strongly energy is emitted in particular directions, how well polarization is preserved and how sensitive the receive chain is to weak echoes.
EMC within the instrument suite
Satellites carry multiple sensors in close proximity. Without effective electromagnetic compatibility (EMC), active transmitters could interfere with other instruments’ receivers. Therefore emissions and susceptibility are measured and documented across different operational states.
From component to integration
The antenna is part of a larger instrument package. The test path runs from component‑level checks through integration within the instrument suite to system tests on the satellite model. Mechanical stress (vibration) and thermal cycles are simulated in parallel so the hardware can withstand launch vibrations and temperature changes in orbit.
Importance for climate and Earth observation
Ground‑penetrating radar data reveal subsurface layering — for example ice thickness, internal ice layers, permafrost or sediments. Such data are central to understanding mass loss in ice sheets, the stability of frozen soils and the availability of freshwater in underground reserves. Imprecise antenna characteristics, by contrast, produce artifacts that can lead to misinterpretation.
Challenges in the lab
The setup demands high precision: small deviations in position, alignment or cable routing alter the radiation behavior. All setups are therefore documented exactly. The team must also assess whether deviations stem from the design, manufacturing tolerances or assembly. The environment matters too: mounts, cables and measurement equipment can reflect energy. Absorbers, increased distances or adjusted test geometries help minimize these effects.
Next steps
After successful antenna and EMC tests, the instrument is integrated into the spacecraft platform, the complete system undergoes final tests and then the launch follows. Once in orbit, a calibration phase with real measurements begins. The laboratory results serve as a reference to identify and correct error sources in the satellite data.