The optical surfaces have {TAIL ~ a high value} of elastic modulus, reducing coma and other aberrations associated gravity and {HEAD ~ acceleration} 
The optical surfaces have { TAIL ~ a high value } of elastic modulus , reducing coma and other aberrations associated gravity and { HEAD ~ acceleration }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD