Minimize Iridium PRIME

Iridium PRIME — A Constellation of Hosted Payloads

Overview    Spacecraft    Launch   References

In September 2013, Iridium Satellite LLC of McLean, VA, announced the first turnkey hosted payload solution, Iridium PRIMESM, to host third-party payloads on stand-alone satellites leveraging the global connectivity afforded by the Iridium NEXT satellite network. The Iridium PRIME program revolutionizes the hosted payload business model with an integrated service which reduces the complexity, delays and costs typically associated with building, launching and operating a satellite mission. 1)

Opportunities exist starting in late 2017 for government and commercial customers to host payloads on Iridium PRIME satellites in LEO (Low Earth Orbit). As many as 66 Iridium PRIME satellites will be available for hosting depending on customer demand; hence, there will be a "pipeline" of frequent flight opportunities to serve the needs of multiple customers. Iridium offers hosted payload accommodations on Iridium PRIME under commercial service level agreements. 2) 3) 4)

Iridium PRIME will be the world's first turnkey space payload accommodation service. The customers will use the Iridium PRIME service to:

• Procure and operate on-orbit hosted payload mission capabilities

• Integrate space and ground system network services for payload command and data handling, and

• Utilize interfaces to deliver payload data to the end-user.

Customers who take advantage of the Iridium PRIME standard service can expect to save more than 50% compared to traditional stand-alone satellites, while retaining flexibility in their program's deployment schedule, number of payloads, and position within the Iridium PRIME orbit planes.

The affordability for using the Iridium PRIME service comes from four significant advantages:

1) Commodity Bus from Active Assembly Line. The Iridium PRIME SV (Space Vehicle) bus is derived from the Iridium NEXT SV bus designed for 12.5 years of reliability. Thales Alenia Space in France and their partner Orbital Sciences Corporation in the United States are currently in the process of manufacturing eighty-one space vehicles for Iridium NEXT. The Iridium PRIME SVs are identical to the Iridium NEXT SVs except that Iridium PRIME will not be equipped with the L-band main mission antenna and L-band RF equipment. Consequently, the Iridium PRIME SV will have sufficient capacity to support a single large payload or multiple small to medium-sized payloads.

2) Standard Interfaces. Iridium PRIME leverages standard data and power interfaces on the commodity bus platform. These interfaces keep the accommodation concept simple and cost effective to replicate.

3) Existing Communication Infrastructure. The data paths to and from the hosted payload will use Iridium's globally accessible, space and ground network permitting rapid and continuous data transfer from anywhere on the planet to the customer's facility for payload command, control and data processing. This unique operational advantage frees up resources and talent that the customer would traditionally dedicate to TT&C (Telemetry, Tracking and Control) communication and payload mission data acquisition architectures.

4) Seasoned Satellite Operations Team. The same satellite controllers and network operators who manage Iridium NEXT will also operate the Iridium PRIME SV bus and data communication network. This synergy of purpose within the existing Iridium Satellite Network Operations Center (SNOC) represents a huge cost savings compared to outfitting and managing a separate satellite and network control facility.

Iridium PRIME Capabilities:

Table 1 shows the expected capacity for hosted payloads in terms of mass, volume, power, and data rate. Payload customers will have continuous connectivity for payload command and mission data dissemination through the Iridium mesh network with typically less than 0.5 second delay. Figure 1 shows the volume available for hosted payloads on Iridium PRIME.

Mass of hosted payload

210 kg

Payload dimensions

Two hosted payload volumes are available

Payload power

650 W (1100 W peak)

Payload data rate

1 Mbit/s continuous; surge up to 10 Mbit/s

Data latency

< 0.5 s typical

Table 1: Hosted payload capacity on Iridium PRIME


Figure 1: Nadir-facing volume available for hosted payloads on Iridium PRIME (image credit: Iridium Satellite LLC)

Based on the constraints of launch vehicle fairing diameters, the maximum payload height for payloads mounted on the nadir-facing deck is 50 cm on the Space-X Falcon 9 and 40 cm on the Kosmotras Dnepr. Figure 2 provides dimensions of volume available for hosted payloads in stowed configuration for the Falcon 9 and Dnepr. The red volume is dedicated to hosted payloads; the dark blue volume is also available for expanded hosted payload access but impact on space vehicle assembly, integration and test processes will need to be assessed.



Figure 2: Iridium PRIME stowed hosted payload capacity on Falcon 9 (left) and on the Dnepr launch vehicle (right), image credit: Iridium Satellite LLC)




Iridium PRIME will take advantage of the Iridium NEXT bus platform (referred to at Iridium as the "commodity bus"), designed for 12.5 years of reliability. The bus platform capacity and power that will be used by the primary telecommunications mission on the 81 original Iridium NEXT spacecraft can now be used by the hosted payload customers on Iridium PRIME. The Iridium PRIME platform will benefit from Iridium's ISLs (Intersatellite Links), allowing each hosted payload to enjoy near- realtime connectivity through the Iridium spaceborne mesh network with typically less than 0.5 second delay for payload commanding or for data transmission.

A description of the Iridium PRIME spacecraft will be added when available later on in the Iridium PRIME Space Vehicle User Manual.


Communication architecture:

Iridium PRIME space vehicles will each be equipped with four inter-satellite links and two feeder links compatible with the Iridium spaceborne mesh network, thereby enabling continuous connectivity for payload commanding and data dissemination. Hosted payload data will be distributed to the end-user through the same space and ground infrastructure supporting all other Iridium telecommunications services.

The mission data and telemetry from hosted payloads will be transmitted from the host spacecraft via K-band crosslinks to the Iridium SV passing overhead the ground teleport. The payload data downlinked to the teleport will then be routed via managed network services to the Iridium PPOC (PRIME Payload Operations Center) located at the SNOC. Inside the PPOC, the payload data will be routed to the customer's access router located at the SNOC. From the access router, the customer will be able to multi-cast the data to as many destinations as desired. Commands to the hosted payload will be routed in a similar fashion from the customer's payload operations and control center to the customer's access router at the SNOC and then on to the destination payload. The typical latency of these paths is expected to be less than 0.5 seconds.

As shown in Figure 1, each Iridium PRIME SV will provide the complement of hosted payloads at least 1 Mbit/s of continuous connectivity through the Iridium spaceborne mesh network. Depending on the amount of data being transferred elsewhere in the network, as much as 10 Mbit/s of surge capacity may be available for temporary periods of time.

In order to be integrated within and able to take advantage of Iridium NEXT's global spaceborne mesh network and ISLs, Iridium PRIME satellites will fly at the same orbit altitude and inclination as the Iridium NEXT satellites. Table 2 displays the orbit specifications. In this orbit, Iridium PRIME can support up to 100 percent global coverage. From the vantage point of its 86.4 degree inclined orbit at 780 km altitude, each Iridium PRIME satellite will expose payloads with horizon-to-horizon fields of regard to every part of the planet. Payloads on additional satellites can improve revisit time to hours, minutes, or even constant coverage with 66 hosts.


Business approach:

Iridium recommends three three incremental steps, based on experience of hosting payloads commercially for other customers, so that each party is fully aware of the mission requirements and technical risks.

Step 1: Complete Payload Questionnaire. Hosted payload customers can take steps to develop a hosted payload mission and service level agreement by completing a payload questionnaire. The questionnaire collects general program and payload information regarding physical properties, requirements, and interface details. This information will inform discussions about the feasibility of the payload accommodation and identify any critical questions and issues that warrant further examination. If a customer-funded study is needed to address any critical questions and issues, the objectives of that study should be defined during this step. The questionnaire can also help Iridium determine if other compatible payloads can be co-manifested on the same bus platform with the customer's payload.

Step 2: Funded Study. If necessary, Iridium will complete a customer-funded study to examine specific areas of accommodation design or risk. The scope of the funded study can be tailored to:

- Develop preliminary physical accommodation layout and interfaces for the desired hosted payload(s)

- Quantify the non-recurring engineering needed to resolve any identified challenges of a particular hosted payload accommodation

- Refine the specific details of an interface requirements document

- Refine the specific details of an interface requirements document.

Step 3: Finalize Hosting Agreement and Data Transmission Services Agreement. After resolving any issues during the funded study, the customer and Iridium can sign a hosting agreement and a data transmission services agreement.

Hosting Agreement. The hosting agreement covers the scope of activities before launch and during early operations and checkout including:

- Procurement of the commodity bus platform

- Accommodation design for the hosted payloads

- Space Vehicle Integration and system level testing

- Connectivity between the payload and the customer's access router

- Launch services including early operations and checkout.

Payloads are assumed to be customer furnished, so cost of the payload is not included in the hosting fee.

The hosting agreement will reference a Hosted Payload Mission Specification that documents how the SV accommodations and ground systems comply with the requirements of the customer's mission requirements document. This specification will govern the performance of Iridium's space and ground accommodations in support of the hosted payload mission, including the volume, mass, power, and data connectivity allocated to the hosted payload. The hosting agreement will also define the hosting fees and payment schedule, responsibilities, ground rules and governance, and the data packages that the customer shall deliver to show compliance of the payload with the Iridium PRIME bus interface and environmental requirements.

For multi-payload missions, the portion of the hosting fee allocated to each customer will be based on the portion of space platform resources (mass, power, volume, data access, and operational priority) that any particular payload uses. This fee will be billed according to a payment schedule negotiated by the parties to the contract.


Launch: A first launch of the Iridium PRIME series is planned for 2017. Iridium's notional schedule for PRIME is to keep the commodity bus assembly rolling along after the NEXT program has completed its assembly run and to start launching PRIME satellites six months after the last NEXT satellite has launched with a Q4 2017 as the target timeframe.

Iridium NEXT is Iridium's next generation satellite constellation of 66 satellites with 6 onorbit spares and 9 ground spares. The NEXT constellation will be deployed between 2015 and 2017 on SpaceX Falcon 9's and the Russian Dnepr, the converted Russian ballistic missile. The Falcon 9 can launch 10 Iridium satellites at one time while Dnepr can launch two.


Figure 3: Schedule of deployment activities for Iridium NEXT and Iridium PRIME. Iridium PRIME launch opportunities continue until 2030 (image credit: Iridium Satellite LLC)

Orbit descriptor



6028 seconds (~100.5 minutes)



0.00126Argument of perigee




Average altitude

780 km

Table 2: Iridium orbit description


Data Transmission Services Agreement. The Data Transmission Services Agreement will cover the services during routine on-orbit operations including:

• Command and control of Iridium PRIME SV including tracking, station keeping, space vehicle planning, anomaly resolution, arbitration of bandwidth and power usage by multi-payload missions, and network operations, planning, and maintenance.

• Continuous access to 1 Mbit/s by the complement of hosted payloads on each SV. For multi-payload missions, allocation of bandwidth for each customer will be defined in the Data Transmission Services Agreement.

For multi-payload missions, the data service and operations fee will be apportioned to the various customers based on the relative use of data services and operations support.

In conclusion, Iridium PRIME, with its global coverage approach, can support a variety of potential missions including:

- Earth observation

- Terrestrial and space weather

- Scientific missions

- Climate monitoring

- Advanced broadband services

- Automatic identification services

- Inter-satellite control and data links

- Cosmic observatory missions

- Space situational awareness

- Prototype demonstrations.

Iridium is ready to leverage its established spaceborne mesh network, ground infrastructure, and flexible bus design to supply affordable, responsive solutions in LEO with Iridium PRIME, the world's first turnkey payload accommodation service.


1) Diane Hockenberry, "Iridium Revolutionizes Delivery of Space-based Services with First Turnkey Hosted Payload Program, Iridium PRIMESM,Iridium Press Release, Sept. 9, 2013, URL:

2) David A. Anhalt, "Affordability Advantages Favoring the Iridium PRIME Payload Accommodation Service," Proceedings of the 65th International Astronautical Congress (IAC 2014), Toronto, Canada, Sept. 29-Oct. 3, 2014, paper: IAC-14-D1.7.1

3) Jeff Foust, "Profile: David Anhalt, Vice President and General Manager, Iridium Prime," Space News, Nov. 1, 2014, URL:

4) "Iridium PRIME - A Revolutionary Approach to Hosted Payloads," Iridium, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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