Frequently Asked Questions
- What is a Geostationary satellite? Satellites in geostationary orbit (GEO) move above the equator at the same speed as Earth’s rotation, taking 23 hours, 56 minutes, and 4 seconds to complete one orbit. This makes them appear stationary over a fixed spot. They travel at about 3 km per second at an altitude of 35,786 km, much higher than many other satellites.GEO is used for satellites that need to stay above a specific location, like telecommunication and weather satellites. This allows ground antennas to remain fixed, always pointing at the same satellite. GEO satellites cover large areas, so only three equally spaced satellites are needed for near-global coverage, similar to seeing more of a map from farther away. Read more about this in the ESA article here.
- What is a Polar Orbiting satellite? Satellites in polar orbits travel north to south, passing over or near Earth’s poles. These low Earth orbits range from 200 to 1000 km in altitude. A sun-synchronous orbit (SSO) is a special type of polar orbit where satellites stay synchronized with the Sun, passing the same spot on Earth at the same local time each day. This is useful for monitoring changes over time, such as weather patterns, emergencies like forest fires, or long-term issues like deforestation. SSOs usually maintain constant dawn or dusk positions to avoid Earth’s shadow, with altitudes between 600 and 800 km and speeds around 7.5 km per second at 800 km. Read more about this in the ESA article here.
- What is a Polar Plot? A polar plot is a type of graph used to represent data in terms of angles and distances from a central point. It is particularly useful for displaying elevation and azimuth angles. For a ground station, a polar plot can be used to show the users where a satellite or object is located in the sky, helping to visualize its position and movement relative to the station.
- What is Azimuth? Azimuth is the angle between the direction of an object and a reference direction, usually true north, measured clockwise around the observer’s horizon. It is commonly used in navigation, astronomy, and satellite communication to specify the direction of an object in the sky.
- What is Elevation? Elevation is the angle between the horizontal plane and the line of sight to an object, usually measured in degrees. It is used to specify how high an object is in the sky, with 0 degrees being at the horizon and 90 degrees being directly overhead.
- What is Field of View? A ground station’s field of view is the portion of the sky its antennas can cover for satellite communication, defined by its elevation angle, azimuth range, local obstructions, and the antenna’s tracking capability. Local obstructions, such as buildings, trees, and mountains, can block or interfere with signals, reducing the effective field of view by limiting the angles at which the ground station can maintain clear communication with satellites. This often necessitates positioning antennas at higher elevation angles or choosing locations with minimal obstructions.
- What is Signal-to-Noise Ratio (SNR)? Signal-to-Noise Ratio (SNR) is a measure used in communications and signal processing to quantify the ratio between the power of a signal and the power of background noise. It is typically expressed in decibels (dB). A higher SNR indicates a clearer, more distinguishable signal with less noise interference, leading to better communication quality and data accuracy.
- What is Sample Rate? Sample rate, also known as sampling rate or sampling frequency, is the number of samples of a continuous signal taken per second to represent the signal digitally. It is measured in samples per second (Hz). Higher sample rates allow for more accurate representation of the original signal, capturing more detail, but also require more storage and processing power.
- What is a target satellite? A target satellite is a specific satellite that a ground station aims to communicate with or track.
- What are waypoints? Waypoints are used by the SatTrackPredictor Tool to predict where the target satellite will be relative to the selected ground station. These waypoints can be used to direct the selected ground station where to point its antennas for optimal communication with the satellite.
- What is a time slot? A time slot is a 10-minute window where you can reserve a ground station for a satellite link.
- Why are recording times limited to 4 minutes? The MVP service limits the total recording time to 4 minutes. Future revisions will increase this duration. Four minutes is currently considered sufficient time to receive a signal and complete the exercises.
- How are results for a pass request shared? Results from your pass request are shared via Dropbox. Once the results are ready, the contact email will be sent to the link to access the results.
- How long does it take to receive the results of a pass request? Results from a pass request are sent to the contact emails address within 1 hour after the booking time.
- How long does it take to receive confirmation of a pass request? Submitted pass request orders are checked before being accepted, this can take up to 1 hour after ordering.
- Why do I need to book slots which are at least 30 minutes in the future? The current MVP service requires a minimum of 30 minutes to process an order and schedule it with a given ground station. It is possible to book slots less than 30 minutes into the future but they may be rejected or missed.
- Why was my order rejected? If your email has been rejected, check the reservation email you received. Most likely a value was not submitted correctly or was missing.
- Error 403? If this error occurs, take the following steps:
- Refresh the page (Ctrl + F5)
- If this does not resolve the issue, close the tab and revisit the Dashboard after 4 hours.
- What are waypoints? Waypoints contain information about the satellite’s position relative to the ground station, including latitude (Lat), longitude (Lon), altitude (Alt), range, azimuth (Az), and elevation (Ele). They are crucial for guiding the ground station’s antennas to establish optimal communication with the satellite.
- How to estimate SNR using baseband recording? Using your RF spectrum plot from the program SDR# of your recording, estimate the power of the signal and the noise floor. The SNR in dB is the dB difference between the peak signal and the noise floor.
- How to estimate the station misalignment? To find the estimated misalignment of the dish, sweep across a target signal while keeping either the elevation or azimuth constant. Using the baseband recording, note the rotor position once the signal reaches a minimum signal strength (SNR). Additionally, note the rotor position once the signal falls below this minimum SNR. Estimate the beam centre point (Azi/Ele) between these two recorded positions and compare it with the satellite’s calculated position. This method will give you an indication of any misalignment.
- Why are some azimuth values negative in my results log? The rotor has an operational range of -180 degrees to 540 degrees. In certain cases the azimuth angle may be displayed in the negative form. Add 360 degrees to negative values if necessary.
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