The Communications Payload 1231 The transponder system

Figure 12.16 is a simplified block diagram of a typical satellite repeater, which together with its associated antenna subsystem would make up a complete on-board transponder. Low-noise amplifier Down converter Low-noise amplifier Down converter Demultiplexer Level Up converters Transmitters Figure 12.16 A simple on-board repeater Demultiplexer Level Up converters Transmitters Figure 12.16 A simple on-board repeater Depending on the purpose of the satellite, there may be just one or perhaps...

The spinning spacecraft

The dynamics of a spinner are covered in Section 3.4.2 of Chapter 3. It is assumed here that the vehicle is spinning about its z-axis with an angular rate S, and that its mass distribution is axially symmetric so that w. The response to a torque will be of interest in one or both of the two sets of axes. A typical 'spinner' is shown in Figure 9.4. The response in axes fixed in the structure will be of interest when the torque components are in these axes or when the attitude sensors measure...

Cots Components In The Space Environment

The space environment (see also Chapter 2) can be particularly harmful to COTS devices. Once in orbit, the devices will experience high-vacuum conditions, potentially extreme hot or extreme cold temperature conditions, and relatively high levels of ionizing radiation. Many COTS parts contain plastic materials, which may out-gas under vacuum (see Section 2.4.1 of Chapter 2). These either cannot be flown or require further encapsulation before they can do so. The plastics used to encapsulate...

Microsatellite Platforms

The first modem microsatellites such as UoSAT-1, shown in Figure 18.7, used a conventional mechanical structure with electronic module boxes clustered around a central thrust column. Solar panels were body-mounted to stringers supported from the end (Z-facet) honeycomb panels. However, the need to accommodate a variety of payload customers within a standard launcher envelope, coupled with increased demands on packing density, electromagnetic compatibility, economy of manufacture and ease of...

Intelsat VI spacecraft design

The two consortia bidding for the Intelsat VI contract proposed very different solutions based on their particular expertise. Ford proposed a three-axis-stabilized solution like their Intelsat V design, although considerably larger, to accommodate the larger antennas and the higher power required. Hughes proposed a spinning spacecraft with a despun platform like the Intelsat IV solution. In April 1982, Hughes was awarded a 700 million contract to build five satellites with an option for six...

Info

Clearly, the A V impulses for controlling inclination are appreciably greater than those needed for longitude, and their errors due to cold starts will therefore represent a smaller percentage error. Latitude manoeuvres imply a change of the orbit plane. Such manoeuvres must be performed on the line of nodes, using north south burns at times of day indicated by Table 5.5. Ideally, the thrust vector should be perpendicular to the plane bisecting the initial and required orbit planes (see...

Tracking and data relay satellite system TDRSS

In the early 1980s, NASA set up space-based systems for Tracking, Telemetry and Command TT amp C between ground and space, with the tracking and data relay satellite system TDRSS . TDRSS comprises six operational satellites and one in-orbit spare. The operational ones are separated by 130 of longitude, two at 41 W and two at 171 W, and axe 22.5 45 east-west 310 61 north-south for 100 coverage for both MA and SA users Figure 14.4 TDRSS configuration and coverage limits Required SA J J antenna...