Fig. 1. Spatio-temporal joint cumulative data matrix

Fig. 2. Data processing procedure

Fig. 3. Simulation curves of cumulative time versus the signal-to-noise ratio and detection probability under coherent and incoherent time accumulation. (a) Signal-to-noise ratio; (b) detection probability

Fig. 4. Simulation curves of the number of apertures versus the signal-to-noise ratio and detection probability under coherent and incoherent spatial accumulation. (a) Signal-to-noise ratio; (b) detection probability

Fig. 5. Structure of the time accumulation experiment

Fig. 6. Pre-accumulation versus postcoherent and noncoherent time accumulation corresponding spectrograms

Fig. 7. Plot of integration time versus signal-to-noise ratio and probability of detection for coherent and incoherent time accumulation at 9 fW power. (a) Signal-to-noise ratio; (b) detection probability

Fig. 8. Structure of the space accumulation experiment

Fig. 9. Experimental setup

Fig. 10. Pre-accumulation versus postcoherent and noncoherent spatial accumulation of the corresponding spectrograms

Fig. 11. Plot of the number of apertures versus the signal-to-noise ratio and probability of detection for 2.8 fW power and 1 ms accumulation time in coherent and incoherent spatial accumulation. (a) Signal-to-noise ratio; (b) detection probability

Fig. 12. Signal frequency point amplitude change during iteration process

Fig. 13. Signal-to-noise ratio versus accumulation time and number of apertures under joint spatio-temporal coherent accumulation