A Laser Communication Experiment Utilizing the ACT Satellite and an Airborne Laser Transceiver

The launch o f a l a s e r communication t r a n s m i t t e r package i n t o geosynchronous e a r t h o r b i t onboard the Advanced Communications Technology ( A C T ) s a t e l l i t e w i l l p resen t an e x c e l l e n t o p p o r t u n i t y f o r t h e exper imenta l r e c e p t i o n o f l a s e r communication s i g n a l s t r a n s m i t t e d from a space o rS i t . The ACTS l a s e r package inc ludes b o t h a heterodyne t r a n s m i t t e r ( L i n c o l n Labs des ign ) and a d i r e c t d e t e c t i o n t r a n s m i t t e r (Goddard Space F l i g h t Center des ign ) w i t h b o t h s h a r i n g some common o p t i c a l components. NASA Lewis Research C e n t e r ' s Space E l e c t r o n i c s D i v i s i o n i s p l a n n i n g t o pe r fo rm a space communication exper iment u t i l i z i n g the GSFC d i r e c t d e t e c t i o n l a s e r t r a n s c e i v e r . w i l l be i n s t a l l e d w i t h i n an a i r c r a f t p rov ided w i t h a g l a s s p o r t f o r t h e recept i o n o f the s i g n a l . Th i s paper desc r ibes t h e exper iment and t h e approach t o p e r f o r m i n g such an exper iment . The l a s e r r e c e i v e r Descr ibed a r e t h e c o n s t r a i n t s p laced upon the NASA Lewis exper iment by t h e performance parameters o f the l a s e r t r a n s m i t t e r and by t h e ACTS s p a c e c r a f t o p e r a t i o n s . The conceptual des ign o f the r e c e i v i n g t e r v i n a l i s g i v e n ; a l s o i n c l u d e d i s t he a n t i c i p a t e d performance c a p a b i l i t y o f t h e d e t e c t o r . INTRODUCTION I n r e c e n t years , t h e i n t e r e s t i n u s i n g a modulated l a s e r beam as a spaceborne communications t r a n s p o r t medium has been growing s t e a d i l y as ev idenced by the number o f t e c h n i c a l a r t i c l e s pub l i shed . What has been l a c k i n g has been t h e o p p o r t u n i t y for hands-on exper ience w i t h such systems. n i c a t i o n s Technology S a t e l l i t e , a p r o j e c t of NASA Lewis Research Center w i t h e x t e n s i v e i n d u s t r y p a r t i c i p a t i o n , i s scheduled fo r launch i n t h e s p r i n g o f 1991. I t i s p lanned t o have on-board a l a s e r communication package. i n the package w i l l be a heterodyne l a s e r t r a n s c e i v e r , a p r o j e c t o f L i n c o l n Labs, and a d i r e c t d e t e c t i o n l a s e r t r a n s c e i v e r , a p r o j e c t o f NASA Goddard Space F l i g h t Center . Also i n c l u d e d w i l l be an a c q u i s i t i o n and t r a c k i n g system, be ing implemented by L i n c o l n Labs. r e c e i v e r i n geosynchronous o r b i t w i l l o f f e r exper imenters a r a r e o p p o r t u n i t y f o r hands on a c t i v i t i e s w i t h l a s e r communication systems. I t i s t h e c u r r e n t i n t e n t i o n o f NASA Lewis ' Space E l e c t r o n i c s D i v i s i o n t o pe r fo rm a s e r i e s o f exper iments u t i l i z i n g t h e d i r e c t d e t e c t i o n l a s e r package on ACTS. w i l l d e s c r i b e SED'S approach t o p e r f o r m i n g t h e exper iment , and a b r i e f d e s c r i p t i o n o f t h e c a l c u l a t i o n s i n v o l v e d . The Advanced Commu-