Profits of Commumications Satelite Corp. declined about 16 percent last year under the impact of a government decision affecting international satellite rates, the Washington company reported yesterday.

Despite a substantial increase in overall business volume and higher profits from a subsidiary, Comsat General Corp., Comsat's total profits fell to $32.5 million ($3.27 per share) compared with $38.3 million ($3.83) in 1976.

The firm's earnings wopuld have exceeded those of 1976 but for a Federal Communications Commission proceeding related to international rates. In both 1977 and 1976, orifuts were affected adverwsely by a requirement for Comsat to set aside funds in an escrow acount equal to satellite use charges abouve that advocated by the FCC.

Since the escrow requirement was in effect for only about half of 1976, however, the reduction in revenues was far greater for Comsat last year - by $38 million.

Comsat said leases of full-time half circuits to its customers for the international satellite communications system in which the company participates as U.S. representative increased 19 percent in 1977.

Total revenues jumped $14.5 million to a record $168 million, mainly because of operations of the Comsat General subsidiary's satellite systems. Comsat General contributed 65 cents a shcre to 1977 earnings compared with 16 cents in1976 as sales rose to $61.5 million from $28.5 million.

As reported earlier, Comsat lawyers and representatives of the FCC's Common Carrier Bureau recently agreed to a proposed settlement to the long Comsat rate controversy - generally putting into effect the lower rates but adding to the company's investment base for rate-setting purposes.

The accord is subject to full FCC approval after a period for public comment expires March 30.

Comsat's net income per shate figure for 1977 was computed on the basis of 9.9 million shares - the average of shares outstanding for the full year. In December, the firm purchased 2 million of the shares as an initial step in restructuring Comsat's financial base.

The earnings statement excluded form consolidated operations the amounts of money Comsat put into the escrow fund - $92.2 million plus interest of $3.5 million that will be distributed to international communications firms that buy satellete services from the Washington company.

Under the proposed FCC-Comsat accord, the company will relinquish all claims to these funds and the regulatory agency will be left with a decision on how the refunds are to be distributed to Comsat's customers.

Comsat's assets at year-end totaled $597 million compared with $590 million a year earlier.

Tesdata Systems Corp., of McLean, reproted a 46 percent increase in profits during 1977 on a 39 percent rise in sales.

Earnings of athe company, which develops methods of monitoring large computer systems, totaled $1.94 million ($1.64 a share) compared with $1.32 million ($1.44) in 1976, with 25 percent more shares outstanding in 1977.Revenues were $14.5 million compared with $10.4 million.

President Thomas E. Stone said Tesdata's results reflected growing acciptance throughout the world of computer monitoring services. He forecast a record year in 1978 for the firm, which sold an initial offering of common stock to the public last April.