Tips for a successful mission

In the previous two posts in this series, we discussed the sources of geometric and radiometric anomalies and how FarEarth corrects for them. 

In this blog, we share tips to make your mission a success.  

Accurate satellite attitude control

Smaller satellites are agile. Your satellite will change orientation and frequently capture images from almost anywhere on Earth, even when not flying directly over the area of interest (AOI).

The first hurdle is pointing the satellite correctly while keeping the imaging instrument aligned. This is especially difficult for a push-broom camera where the scanline must remain perpendicular to the flight path. Failing this, pixels can smear, especially with TDI or binning.

You need accurate attitude control while maintaining a suitable orientation of the imager, so you never miss your target. 

Accurate and frequent position and orientation data

Once your satellite is correctly oriented, precise angles are essential. Satellites may drift; attitude measurements may be inaccurate, and therefore, frequent updates of the satellite's position (ephemeris or GPS) and attitude (orientation) are necessary. 

You need to ensure that you get position and attitude information as accurately as possible, at least 10 times per second. 

Remember to provide 3 seconds of position and attitude information before and after the imaging period. This will help to model the flight path and movement accurately to the first and last pixels.

Keep the satellite steady 

You should plan for the satellite to reach the final orientation 10 seconds before imaging begins. This time allows any over- or under-damping during manoeuvring to settle. 

Once acquisition starts, you must control yaw to keep the sensor properly aligned (referred to as yaw-steering). If you are not implementing forward motion compensation techniques, you should remember to keep the pitch and roll stable during image acquisition.

Maintain the correct instrument temperatures

Satellite instruments are designed to operate under specific thermal conditions. When a camera is not within the proper temperature range, thermal expansion can negatively affect the alignment of optical components, causing focusing problems.

Ensure that you can control the temperature of your instruments using the appropriate combination of heat sinks or sources. During your mission planning phase, consider the time required to heat an instrument to the correct temperature before the planned acquisitions. 

Keep the off-nadir angles low and the Sun high 

You may want to acquire imagery at angles beyond 20 degrees. In some cases, especially for time-sensitive acquisitions, this can be the best course of action.

However, large off-nadir acquisition angles can introduce severe distortions in the imagery and push the target outside the ideal focal depth.

Consider the Sun's angle. In high latitudes, the Sun may be very low to the horizon during certain times of the year. When possible, keep the Sun high above the horizon to ensure that the imager receive enough light. FarEarth’s product metadata includes these angles to help you and end users understand conditions during image acquisition.

FarEarth’s Level 0 Reports

FarEarth’s Level 0 Product Report contains details that visualise the aspects discussed. You will find the report useful during commissioning to track your satellite’s behaviour.

Hope you enjoyed this read!