# Discoverer 21

> Reconnaissance satellite

**Wikidata**: [Q5281804](https://www.wikidata.org/wiki/Q5281804)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Discoverer_21)  
**Source**: https://4ort.xyz/entity/discoverer-21

## Summary
Discoverer 21 was a reconnaissance satellite launched on February 18, 1961. It was deployed into orbit using a Thor-Agena B rocket launched from Vandenberg Space Launch Complex 1. As part of the Discoverer program, its role was to covertly collect data for intelligence or military applications.

## Key Facts
*   **Classification:** Discoverer 21 is an instance of a reconnaissance satellite, a class of satellite designed to covertly collect data for intelligence or military applications.
*   **Launch Date:** The satellite was launched on February 18, 1961.
*   **Launch Vehicle:** It was launched aboard a Thor-Agena B, an American orbital launch vehicle.
*   **Launch Site:** The launch originated from Vandenberg Space Launch Complex 1.
*   **COSPAR ID:** The satellite holds the international designation 1961-006A.
*   **Satellite Catalog Number:** It is tracked under Satellite Catalog Number (SCN) 00084.
*   **Significant Event:** The deployment of the satellite is categorized as a rocket launch event occurring at Vandenberg Space Launch Complex 1 on February 18, 1961.

## FAQs
### Q: What was the primary function of Discoverer 21?
A: Discoverer 21 functioned as a reconnaissance satellite. Its purpose was to covertly collect data for intelligence or military applications.

### Q: When and where was Discoverer 21 launched?
A: The satellite was launched on February 18, 1961, from the Vandenberg Space Launch Complex 1.

### Q: What rocket was used to launch Discoverer 21?
A: Discoverer 21 was launched using a Thor-Agena B rocket, which is classified as an American orbital launch vehicle.

### Q: What are the unique identifiers for Discoverer 21?
A: The satellite is identified by the COSPAR ID 1961-006A and the Satellite Catalog Number 00084.

## Why It Matters
Discoverer 21 serves as a historical example of early space-based intelligence gathering infrastructure. Launched in 1961, it represents the era of the Cold War where orbital reconnaissance was a burgeoning technology critical to national security. By utilizing the Thor-Agena B—an American orbital launch vehicle—the mission contributed to the development of reliable launch systems for military payloads.

The satellite's launch from Vandenberg Space Launch Complex 1 highlights the strategic use of the West Coast for inserting payloads into polar or near-polar orbits, which is optimal for global reconnaissance coverage. As a reconnaissance satellite, Discoverer 21 played a role in the transition from traditional aerial surveillance to orbital monitoring, allowing for the covert collection of data without the risks associated with manned overflights. Its specific mission objectives are classified under the umbrella of intelligence applications, but the technical details of its launch and vehicle type provide insight into the aerospace engineering capabilities of the United States during the early 1960s.

## Notable For
*   **Early Reconnaissance:** It is an early example of an American reconnaissance satellite designed for intelligence gathering.
*   **Specific Launch Vehicle:** It utilized the Thor-Agena B, a distinct American orbital launch vehicle configuration.
*   **Low Catalog Number:** It possesses a very low Satellite Catalog Number (00084), indicating its placement in the earliest era of tracked space objects.
*   **Vandenberg Origin:** It is associated with the historic Vandenberg Space Launch Complex 1, a primary site for military space launches.

## Body

### Mission Classification
Discoverer 21 is officially classified as a **reconnaissance satellite**. In the context of the provided knowledge, this class of satellite is defined by its ability to covertly collect data for intelligence or military applications. The satellite is a documented instance of this technology, representing a specific mission within the broader scope of space-based surveillance.

### Launch Operations
The satellite's deployment was executed on **February 18, 1961**. This event is logged as a significant "rocket launch" event.
*   **Location:** The launch took place at **Vandenberg Space Launch Complex 1**. This site is a key geographic marker for the mission's origin.
*   **Vehicle:** The launch was facilitated by the **Thor-Agena B**. This vehicle is explicitly categorized as an American orbital launch vehicle, linking the satellite to a specific lineage of U.S. aerospace technology.

### Technical Identifiers
Discoverer 21 is cataloged in multiple scientific and academic databases using the following identifiers:
*   **COSPAR ID:** `1961-006A`
*   **Satellite Catalog Number (SCN):** `00084`
*   **Wolfram Language Entity Code:** `Entity["Satellite", "00084"]`
*   **Freebase ID:** `/m/0ch34ml`

These identifiers allow for the precise tracking and referencing of the satellite across different knowledge systems, including Wikidata and Wolfram Language datasets. The satellite is also referenced in Greek (`el`), English (`en`), and Polish (`pl`) language Wikipedia articles.

## References

1. Jonathan's Space Report