Start with the observation question

Gao Fen 1-01, commonly called Gaofen-1, launched in 2013 as part of China’s High-Resolution Earth Observation System, often called CHEOS. Its applications include land monitoring, environmental study and disaster assessment. A complete observing service needs spacecraft, ground reception, processing and people who can interpret the result. A launch is one milestone in that chain.

This course follows the civilian Gaofen-1–7 examples documented in a 2022 research review. Those examples explain complementary instruments; they are not a count of every satellite carrying the Gaofen name or a statement about which spacecraft are healthy today. A dated program description also needs careful reading: a forecast is not evidence that a capability was later delivered.

Spatial resolution concerns distinguishable ground detail. Spectral resolution concerns which wavelength ranges are separated. Temporal sampling concerns when repeat observations are available. A task may need a useful balance of all three. The smallest quoted pixel alone does not tell you whether the instrument measures the right property at the right time.

Consider an original planning exercise: a team needs to follow a spreading event several times during a day, while another needs a detailed boundary map afterward. The first needs timely repeat coverage; the second needs suitable spatial detail and comparison data. A sharper image arriving after the decision deadline may be less useful for the first task.

Choose observations for the question

Gao Fen 1-01 provides optical imagery, while Gao Fen 3 carries a C-band radar. The reviewed series also includes Gaofen-4 geostationary imaging, Gaofen-5 spectral and atmospheric measurements, and Gaofen-7 stereo mapping with laser ranging. Their products answer different questions; do not apply one satellite’s measurement method to all of them.

Write an observation request before choosing hardware: name the location, time window, quantity to estimate, minimum useful detail and acceptable missing-data rate. Then ask how the result will be checked. This makes it possible to choose complementary observations rather than selecting whichever image looks most impressive.