Types of capacity

Satellite capacity is broadly divided into distribution and contribution. Distribution capacity is used to deliver signals to cable head-ends or transmitters for terrestrial distribution, or for DTH satellite delivery. Contribution capacity provides routes for transmitting material from point-to-point (generally) for inclusion in distributed programmes after (usually) some production process.

There are several different types of satellite capacity that can be accessed by SNG uplinks, and satellite system operators broadly classify these as follows:

The type of capacity determines, in a number of ways, the method of working for an SNG uplink (this is true whether it is a truck or flyaway system). An uplink can access capacity which covers a number of the above types – for instance, it could have a booking for ‘occasional’, ‘dedicated’ capacity, which might be in inclined orbit.

Dedicated and non-dedicated capacity

The term used for capacity on a satellite that has been specifically set aside for a particular purpose is dedicated capacity. So for instance, on Intelsat and Eutelsat satellites, there is dedicated capacity allocated individually for services such as business data, video, audio and radio services, public telephony, paging and messaging, and Internet.

The reason why there is a separation of capacity into dedicated uses is that this allows the satellite operator to optimize the technical parameters of a transponder (or group of transponders) providing a particular service. For instance, a satellite operator may concentrate DTH services on one particular satellite, so that consumers can have their satellite dishes pointed at a single satellite only for a wide range of channels.

SNG places particular demands on the satellite operator. SNG signals tend to be made up of a number of relatively short duration signals of differing power levels, with transmissions starting and ending in an apparently random sequence. Therefore, it too tends to be grouped onto a particular transponder or group of transponders on a satellite. This allows the cycle of transmissions frequently beginning and ending from possibly interfering with other services.

There is an increasing amount of capacity allocated for SNG purposes, which is kept available for occasional traffic. Often the capacity allocated to occasional SNG traffic is capacity not normally required for any other purpose, so non-dedicated capacity is spare capacity that can be used for SNG or any other temporary use on occasions if it is available. Every satellite operator always has some spare capacity available to accommodate in-service failures on satellites, and if the circumstances are right, this capacity may become available for SNG. For instance, if an important news story breaks in a particular area, satellite operators may be prepared to offer capacity not committed to some other service for SNG. It has even been known for a satellite operator to ‘shuffle’ services around to create suitable capacity for SNG, if they perceive that there may be a significant financial advantage (due to demand) in offering SNG short-term capacity on a story.

Capacity may also change from dedicated to non-dedicated at various times. This may be a transponder, or a part-transponder, that is vacant in between the ending of one long-term lease (also sometimes called a full-time lease) and the beginning of the next.

Short-term leases

These are available for short periods – usually one to four weeks – and short-term leases are particularly popular where a major news or sporting event is taking place in an area where interested broadcasters and newsgatherers do not already have leased capacity available. A number of satellite operators made capacity especially available for the Winter Olympic Games in Nagano, Japan in 1996, the ‘hand over’ of Hong Kong in 1997, the Gulf crisis in early 1998, the 1998 World Cup Football, the Sydney Olympics in 2000 and the aftermath of the terrorist attacks on the United States in 2001.

Short-term leases offered on this type of capacity are charged at a higher pro rata rate than long-term leases.

Occasional capacity

This type of capacity is typically used for SNG operations, but occasional (ad hoc) capacity is scarce in some areas of the world, and relatively plentiful in others. For most newsgatherers, the availability of occasional ‘on-demand’ capacity is critical. Even though a newsgathering organization may have leased capacity, a story can break in an area out of the geographical service area of their leased capacity, or create such a demand for feeds that extra capacity needs to be bought in. Smaller newsgatherers may depend totally on being able to access occasional capacity, whether they are global or regional newsgatherers, and this is an important market for satellite operators. However, whenever there is a big news story in a poorly served area, it is often a struggle for satellite operators to meet the demand.

The relative cost of occasional capacity is high in comparison to leased capacity, but it is reasonable when considering the extra work that a satellite operator has to undertake to meet occasional service requests. Bookings are usually of a minimum 10 min duration, extendible in 1 or 5 min increments. It is not unusual for a booking to be placed at less than 15 min notice.

There are high cancellation charges, which are factored depending on how much notice is given before the booking is cancelled. Virtually all satellite operators will demand 100% payment with less than 24 hours notice of cancellation. However, discounts are given for regular periodic bookings, or for a commitment to use a given number of hours of capacity in a month.

Inclined orbit

Satellites of interest for newsgathering purposes are in a geostationary orbit, but the process of sustaining a perfectly maintained geostationary orbit cannot be continued indefinitely. ‘Station-keeping’ manoeuvres consume energy on board the satellite that cannot be replenished, as the thruster motors that correct the position and altitude of the satellite consume the finite reserves of liquid fuel. At a certain point in the life of a satellite, a decision is taken to abandon some station-keeping manoeuvres, as they are not critical to sustaining the correct orbit. When certain station-keeping is abandoned, the satellite is said to be in inclined orbit.

Essentially, as the satellite is ‘observed’ from the Earth’s surface, it no longer appears to be stationary in relation to that point on the Earth’s surface, and requires tracking by both the SNG uplink as well as the downlink earth station. When there is insufficient fuel to even sustain basic station-keeping, the satellite is deemed to be finally terminated and is declared as being at the end of life. Capacity that is completely station-kept – i.e. stable – commands a higher premium than capacity deemed to be in inclined orbit. The disadvantage of inclined-orbit capacity is that the SNG has to constantly track the path of inclination. At the downlink, where the receiving antenna is fairly large (over 3.5 m), this is commonly performed by auto-tracking equipment, which not only gradually moves the antenna to keep the satellite on-beam, but also ‘learns’ the daily cycle so that it is able to predict the direction to move the antenna. In terms of SNG uplink, this tracking has to be performed manually.

Hence this capacity is available at lower cost on satellites that are in the final phase of their operational life. In fact, inclined orbit capacity is attractive for SNG, as the majority of transmissions are point-to-point and typically of short duration, and therefore the particular characteristics of an inclined-orbit satellite can easily be coped with by an experienced SNG operator.