Tracking and Data Relay Satellite launch delay
NASA, Boeing Corp., and United Launch Alliance (The company supplying the mighty Atlas V booster rocket) are presently reviewing the August 3 TDRS-M satellite launch which I will be attending at Kennedy Space Center in Florida. It looks like the S-band antenna had some sort of incident during the spacecraft’s final launch processing before the actual launch. The August 3 launch date does not seem possible at this point in time because the antenna will most likely need replacing.
Any of you who have been involved in some sort of space-related electronics know that these systems and their components go through exhaustive testing to ensure no likelihood of a failure on orbit----there is no longer a Space Shuttle program to capture and repair these very costly satellites, so you don’t want another multi-million-dollar piece of space junk floating around the Earth.
(Image courtesy of NASA)
The TDRS-M satellite carries an S-band phased array antenna to allow simultaneous communications with five other spacecraft, as well as two steerable antennae providing S, Ku or Ka band coverage to spacecraft requiring communications at a higher data rate. It’s this system that has caused a delay in the August 3 launch.
The satellite bus
The TDRS-M, constructed by Boeing based on the BSS-601HP satellite bus, weighs 7,615 pounds fully fueled, with a design life of 15 years. The more advanced 601HP version is capable of "high power", meaning it can support up to 60 transponders for higher communications power and can provide up to 10,000 W of electrical power to all the on-board systems. The TDRS-M, powered by two solar arrays, will generate between 2.8 and 3.2 kW of power depending upon the Solar illumination.
The basic Boeing 601 satellite body is made up of two modules:
- The primary structure which holds all the launch vehicle loads. This section also has the propulsion subsystem, bus electronics, and battery packs
- There is a structure of honeycomb shelves which hold the communications equipment, electronics, and isothermal heat pipes.
The reflectors, antenna feeds, and solar arrays mount directly to the payload module, and antenna configurations can be placed on any of the three faces of the bus.
The bus carries two steerable antennae capable of providing S, Ku and Ka band communications for other spacecraft, with an additional array of S-band transponders for lower-rate communications with five other satellites. The TDRS-M satellite has an R-4D-11-300 engine to provide propulsion. The basic R-4D engine was originally manufactured by Marquardt Corp and used as an attitude control thruster for the Apollo Service and Lunar Modules in the 60s. So, the basic overall design is certainly ‘tried and true’.
The physical antenna has a diameter of 15 feet and is constructed with a flexible mesh reflector which can be folded into a smaller size for launch and then once in orbit, they will spring back to their circular dish form.
When the antenna is designated for the S-band, here are the frequency bands that are used in satellite communications:
Uplink: 2.025 to 2.110 GHz
Deep-Space Uplink: 2.110 to 2.120 GHz
Downlink: 2.200 to 2.290 GHz
Deep-Space Downlink: 2.290 to 2.300 GHz
The antenna on the TDRS-M satellite is steerable via a phased array design and is capable of simultaneously transmitting and receiving on the S-band as well as on the Ka- or Ku-band.
See my Planet Analog article for more details on this TDRS-M satellite, entitled: NASA TDRS-M communications satellite.
I am so excited about my upcoming trip to Kennedy Space Center in Florida, to sit so close (as safely possible in the press stands) to the launch pad of the Atlas V. Here’s hoping the launch delay will be relatively short. I will also be getting a behind-the-scenes tour of Kennedy Space Center for an engineer’s look into the electronics that makes the facility perform the Launch Control ‘magic’ that safely guides these massive launch vehicles and payloads into the darkness void of space to perform their duty.
Stay tuned for my series of exclusive reports and articles on EDN and Planet Analog.
- Shrinking communication satellite subsystems
- Satellite anatomy 101
- Getting more out of our satellites
- How to pre-test your product's antenna