Nonsingular PNG-Based Impact Time Control Guidance with Lower Dependence on Time-to-Go Estimate

Table 1

Comparison of controllable ranges of the desired impact time.

Time-to-go estimation formula	ITCG law in [6]	Proposed ITCG law	Impact time error (s)
Zeroth-order approximation of Equation (38)	N/A^a	35.09 s~38.80 s	<0.4
Second-order approximation of Equation (38)	35.50 s~40.58 s	34.17 s~52.48 s	<10^-3
Fourth-order approximation of Equation (38)	35.50 s~6.17 s	34.15 s~56.69 s	<10^-3
Sixth-order approximation of Equation (38)	35.50 s~48.90 s	34.15 s~58.30 s	<10^-3
Exact solution	35.50 s~infinity	34.15 s~infinity	<10^-3

^aN/A stands for “not applicable.”