ATDRS
Advanced Tracking and Data Relay Satellite
Part of the TDRSS program

ATDRS is the follow-on to the NASA TDRS satellites which provide communications coverage to satellites and manned vehicles in low Earth orbit. The new spacecraft will provide the same S/Ku-Band communications services as the original TDRS vehicles, and will also add Ka-band links. In February 1995, Hughes was awarded a $486.1M contract for 3 ATDRS spacecraft (known as TDRS H, I, J during development). NASA employed several new contracting methods for ATDRS, including the provision that NASA would be reimbursed in the event of a spacecraft failure.

Spacecraft
Based on Hughes HS-601 series bus, with modifications to meet NASA requirements. Upgraded attitude control system, telemetry and command system based on other government satellite systems. Deployable solar arrays provide 2040 W EOL.

Payload
Two Single Access (SA) antennas - each antenna is a lightweight 4.5 m steerable dish incorporating new springback reflector technology. Each dish can have simultaneous S/Ku- or S/Ka-band communications with a single user spacecraft. Maximum receive data rates through these antennas are 300 Mbps for Ku and Ka bands and 6 Mbps for S-band. Transmit data rates are 25 Mbps for Ku/Ka and 300 kbps for S-band. One Multiple Access (MA) S-band receive array - an electronically steerable phased array antenna consisting of patch antennas. The MA array can receive data from up to 5 user satellites simultaneously, with each link supporting up to 3 Mbps. One S-band transmit array - an electronically steerable phased array antenna consisting of patch antennas. This array can transmit data to a single user satellite at a rate of 300 kbps. One Space to Ground Link antenna (SGL) - a parabolic antenna operating at Ku-band that provides the communications link between the satellite and the ground. All customer data is sent through this dish, as are all regular TDRS command and telemetry signals. The antenna is gimballed on two axes.

Country of Origin	United States
Customer/User	NASA, GSFC
Manufacturer(s)	Hughes
Size	21 m x 14 m (deployed)
Launch	Planned on Atlas 2A from ESMC
Orbit	Geosynchronous
Design Life	15 years
Related Sites	TDRSS Quicklook TDRSS Home Page