# Sirius FM-4

> unused satellite radio communications satellite, now on display at the Steven F. Udvar-Hazy Center

**Wikidata**: [Q18484840](https://www.wikidata.org/wiki/Q18484840)  
**Source**: https://4ort.xyz/entity/sirius-fm-4

## Summary
Sirius FM-4 is an unused satellite radio communications satellite, originally owned by Sirius XM and manufactured by Lanteris Space Systems. It is now on display at the Steven F. Udvar-Hazy Center in the National Air and Space Museum.

## Key Facts
- **Class**: Communications satellite
- **Mass**: 1,320 kilograms
- **Dimensions**: 228.6 cm (width) × 508 cm (height) × 292.1 cm (length)
- **Aliases**: Radiosat 4
- **Country of Origin**: United States
- **Owned by**: Sirius XM
- **Manufacturer**: Lanteris Space Systems
- **Spacecraft Bus**: Lanteris 1300
- **Power Source**: Two spacecraft solar arrays
- **Status**: Flight spare, now an exhibit
- **Exhibition Location**: Steven F. Udvar-Hazy Center (since October 2012)

## FAQs
### Q: What was Sirius FM-4 used for?
A: Sirius FM-4 was a communications satellite designed for satellite radio services, though it was never launched and remained unused.

### Q: Where is Sirius FM-4 displayed?
A: The satellite is on display at the Steven F. Udvar-Hazy Center, part of the National Air and Space Museum.

### Q: Who manufactured Sirius FM-4?
A: Lanteris Space Systems manufactured the satellite, using the Lanteris 1300 spacecraft bus.

### Q: What are the dimensions of Sirius FM-4?
A: The satellite measures 228.6 cm in width, 508 cm in height, and 292.1 cm in length.

### Q: Is Sirius FM-4 still operational?
A: No, it is a flight spare and is now a museum exhibit.

## Why It Matters
Sirius FM-4 represents a significant piece of space history, showcasing the evolution of satellite radio technology. As a flight spare, it provides insight into the design and engineering of communications satellites. Its display at the Steven F. Udvar-Hazy Center offers a tangible connection to the space industry, allowing visitors to see firsthand the hardware that powers modern satellite communications. The satellite’s dimensions and specifications highlight the scale and complexity of early satellite radio systems, contributing to the broader understanding of space infrastructure.

## Notable For
- **Flight Spare**: Served as a backup unit, never deployed in orbit.
- **Exhibit Quality**: Preserved in its original condition for public display.
- **Satellite Radio Pioneer**: Demonstrates the technological advancements in satellite-based radio broadcasting.
- **Museum Piece**: Part of the National Air and Space Museum’s collection, accessible to the public.
- **Engineering Legacy**: Reflects the work of Lanteris Space Systems in satellite manufacturing.

## Body
### Overview
Sirius FM-4 is a communications satellite that was never launched, remaining as a flight spare. It was designed for satellite radio services and is now on display at the Steven F. Udvar-Hazy Center.

### Physical Specifications
- **Mass**: 1,320 kilograms
- **Dimensions**: 228.6 cm (width) × 508 cm (height) × 292.1 cm (length)
- **Power**: Two spacecraft solar arrays

### Ownership and Manufacture
- **Owned by**: Sirius XM
- **Manufacturer**: Lanteris Space Systems
- **Spacecraft Bus**: Lanteris 1300

### Exhibition Details
- **Location**: Steven F. Udvar-Hazy Center
- **Date of Exhibition**: October 2012
- **Collection**: National Air and Space Museum

### Historical Context
- **Class**: Communications satellite
- **Status**: Flight spare, never operational
- **Significance**: Represents the space industry’s reliance on backup systems and the preservation of spaceflight hardware for educational and historical purposes.

## References

1. [Source](https://space.skyrocket.de/doc_sdat/sirius-cdr.htm)