# Kosmos 903

> Russian military early warning satellite

**Wikidata**: [Q3399243](https://www.wikidata.org/wiki/Q3399243)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Kosmos_903)  
**Source**: https://4ort.xyz/entity/kosmos-903

## Summary
Kosmos 903 was a Russian military early warning satellite launched on April 11, 1977. As part of the Soviet US-K program, it was designed to assist in the detection of missile launches. The spacecraft was deployed from the Plesetsk Cosmodrome aboard a Molniya-M rocket.

## Key Facts
- **Entity Type:** Russian military early warning satellite; Artificial satellite of the Earth.
- **Satellite Class:** US-K (a series of Soviet and Russian early warning satellites).
- **Launch Date:** April 11, 1977.
- **Launch Time:** 01:38:00.
- **Launch Vehicle:** Molniya-M (Soviet space launcher rocket).
- **Launch Site:** Plesetsk Cosmodrome Site 43.
- **COSPAR ID:** 1977-027A.
- **Satellite Catalog Number (SCN):** 09911.
- **Wolfram Language Entity Code:** `Entity["Satellite", "09911"]`.

## FAQs
### Q: What was the primary mission of Kosmos 903?
A: Kosmos 903 was a military satellite built for the US-K series, designed to provide early warning capabilities for the Soviet Union.

### Q: When and how was Kosmos 903 launched?
A: It was launched on April 11, 1977, at 01:38:00 UTC, using a Molniya-M carrier rocket from the Plesetsk Cosmodrome Site 43.

### Q: How is Kosmos 903 identified in international catalogs?
A: The satellite is identified by the COSPAR ID 1977-027A and the Satellite Catalog Number 09911.

## Why It Matters
Kosmos 903 represents a specific era of Cold War-era space technology utilized for strategic defense. As a component of the US-K (Upravlyaemy Sputnik-Kontinent) constellation, this satellite played a role in the Soviet Union's ability to monitor potential missile threats from space. These satellites were critical for providing the necessary reaction time to detect intercontinental ballistic missile (ICBM) launches, forming a backbone of national security infrastructure during the late 1970s.

The launch of Kosmos 903 also highlights the reliance on the Molniya-M rocket, a workhorse of the Soviet space program, and the utilization of the Plesetsk Cosmodrome for military payloads. By studying entities like Kosmos 903, researchers gain insight into the deployment patterns and technological evolution of early warning systems that preceded modern space-based sensor networks.

## Notable For
- **US-K Series:** Being a confirmed unit within the US-K class of early warning satellites.
- **Molniya-M Deployment:** Utilization of the Molniya-M launch vehicle, a standard for Soviet military and communication satellites of that era.
- **Plesetsk Origin:** Launching from Site 43 at the Plesetsk Cosmodrome, a primary hub for military space launches.
- **1977 Launch:** Serving as a historical data point for the Soviet space program's activities in April 1977.

## Body
### Classification and Purpose
Kosmos 903 is formally classified as an artificial satellite of the Earth and falls under the specific subclass of **US-K** satellites. The US-K series (often known by their NATO reporting name "Oko") were Soviet-era spacecraft designed to detect missile launches using telescopes and infrared sensors. The designation "Kosmos" was a standard Soviet practice used to mask the military nature of defense satellites.

### Launch Specifications
The satellite was successfully launched on **April 11, 1977**, at precisely **01:38:00**. The launch event took place at the **Plesetsk Cosmodrome Site 43**, a high-latitude launch site ideal for placing satellites into the highly elliptical Molniya orbits typically used for early warning and communication systems.

### Launch Vehicle
The delivery system used for Kosmos 903 was the **Molniya-M** rocket. This was a four-stage derivative of the R-7 Semyorka family, specifically optimized for launching payloads into high-energy orbits required for military and deep-space communications.

### Technical Identifiers
In international tracking systems, Kosmos 903 is defined by the following identifiers:
*   **COSPAR International Designator:** 1977-027A
*   **Satellite Catalog Number (SCN):** 09911

## References

1. Jonathan's Space Report