Table 3. Measured optical parameters.

R: radius of curvature; Res PtV: residual peak-to-valley displacement after best-sphere subtraction; Res slope error: residual slope error (r.m.s.) after best-sphere subtraction.

Mirror	R (km)	Res PtV (nm)	Res slope error (rad)
PM1a	42.3	120	0.89
PM1b	10.6	46.5	0.56
PM2a	28.1	135	0.95
PRESTO-LE	29.7	36	0.44
PRESTO-HE	27.1	22	0.45
SW	34	78.5	0.59
VD	154.6	42.3	0.32