# Apollo re-entry guidance

I am referencing chapter 7 of the book "Spacecraft Navigation and Guidance" by Maxwell Noton. Can anyone tell me how to determine control gains C1 and C2 in equation 7.58 and 7.59 in respective chapter?

Constant drag deceleration law(above 50 km altitude)

$$(L/D)_v=(L/D)_1+C1(a-a_{nom}(v))+C2(h_{dot}-h_{nom_{dot}})...7.58$$

Constant descent rate law (below 50 km altitude)

$$(L/D)_v=(L/D)_1++C2(h_{dot}-h_{nom_{dot}})...7.59$$

• I could be wrong, but aren't C1 and C2 just certain coefficients that depend on the geometry of the vehicle? If so, they would be found from experiments. However, there really isn't enough context to figure out what these equations are, and we don't have access to the book. Can you give more context? – Arthur Dent May 12 '17 at 21:26
• No these constants are not related to geometry. Whatever I understood is C1 and C2 are semsitivity gains which are used in closed-loop guidance. But I dont knw how to determine values for these. – Pragati Joshi May 13 '17 at 17:09