Our nanosatellite will measure the electron density of the ionosphere to map how radio frequency (RF) waves are affected.
The importance of the ionosphere comes from its wide utilization in long-distance communications, specifically in over the horizon (OTH) radars. Gathering detailed information about the ionosphere helps account for its effects on RF signals, making communication cheaper and more reliable. Mapping the charge density of the ionosphere has been a longstanding scientific objective, and our team’s unique approach is designed to pave the way for future research.
Scientists currently measure charge density in the ionosphere by transmitting HF radio waves of different frequencies into the atmosphere and receiving the reflected and refracted waves. Since the refraction is a function of the frequency of the signal and the charge density, one may estimate the charge density at different places by considering the time delay between when each frequency was transmitted and when each frequency was received. These instruments are called ionosondes, and graphs of transmitted frequency versus time delay are called ionograms.
Unfortunately, ionosondes’ output data do not provide enough information to completely reconstruct the entire charge density gradient. Ionosonde can measure signals’ time of flight, but they cannot discern what paths the signals take. Existing ionosounding methods estimate charge density as a function of altitude by making simplifying assumptions about the path taken by the signal.
The ionosphere is one of the outermost layers of our atmosphere, filled with ionized gases which reflect radio waves. Additionally, these ionized gases in the ionosphere produce light in a phenomenon called “airglow.”
To measure the ionosphere’s environment, our satellite will be equipped with two payloads: the first payload is a photometer, which will measure the airglow so we can extrapolate data on gas density in the upper atmosphere. Furthermore, we will refine our data by detecting RF waves with an ionosonde receiver. This other payload will monitor RF waves we transmit at different frequencies and determine how they behave in the ionosphere.
Airglow provides vital information on the environment of the ionosphere, namely ion density, electron density, and uncharged atom density. Our optical payload will measure the airglow, allowing us to produce a map of vertical electron densities in the ionosphere. Vertical electron density is exactly what it sounds like: electron densities that travel up through the ionosphere rather than across it. Information on vertical electron density is important because most current information about the ionosphere concerns horizontal electron densities. By collecting vertical data, our map of the ionosphere will be more accurate by accounting for all dimensions. Additionally, the photometer in our satellite will be equipped with a unique filter granting it increased sensitivity. Accurate vertical electron density data from this payload will be compounded with the RF payload to make a detailed 3D map of the ionosphere.
Existing ground-based ionosondes don’t provide enough information to accurately map electron densities within the ionosphere. More refined data can be obtained by transmitting signals to an ionosonde receiver in space. That’s where we come in. The ionosonde receiver in our satellite will record test signals relayed from our ground station once on the signal’s path into the ionosphere, and a second time after the signal bounces off the ionosphere back down to earth. The difference in time separating the points of convergence between the satellite and the signal will then be analyzed to develop a precise map of the ionosphere.