# Step Thirteen / Plymouth Rock 3

> American signals intelligence satellite

**Wikidata**: [Q9293100](https://www.wikidata.org/wiki/Q9293100)  
**Source**: https://4ort.xyz/entity/step-thirteen-plymouth-rock-3

## Summary
Step Thirteen / Plymouth Rock 3 is an American signals intelligence (SIGINT) reconnaissance satellite. It was a small 60 kilogram U.S. Air Force spacecraft launched on 23 October 1964 from Vandenberg Space Launch Complex 4 West aboard an Atlas-Agena D vehicle and reentered the atmosphere on 23 February 1965.

## Key Facts
- Classified as a reconnaissance satellite used for signals intelligence (SIGINT).
- Part of the P-11 American small satellite SIGINT program.
- Launch date: 1964-10-23 (launch time qualifier 18:27).
- Launch site: Vandenberg Space Launch Complex 4 West.
- Launch vehicle: Atlas-Agena D (vehicle/serial indicated as 353D).
- Mass: 60 kilograms.
- Operator: United States Air Force.
- Manufacturer: Lockheed Corporation (spacecraft bus) and HRB Systems (payload).
- COSPAR ID: 1964-068B.
- Significant events: rocket launch from Vandenberg SLC-4W on 1964-10-23; atmospheric entry on 1965-02-23.
- Alternate names / aliases: KH 7-13 Capsule; P-11 4302; P11 4302; Mission 7305/7306; OPS 5063; EHH A4.
- Internal catalog/serial number (scn): 00914.
- Country of origin: United States.

## FAQs
### Q: What was the primary mission of Step Thirteen / Plymouth Rock 3?
A: Its primary mission was signals intelligence (SIGINT) collection as a reconnaissance satellite. It was operated by the United States Air Force as part of the P-11 SIGINT small satellite program.

### Q: When and how was Step Thirteen / Plymouth Rock 3 launched?
A: It was launched on 23 October 1964 at 18:27 (qualifier) from Vandenberg Space Launch Complex 4 West aboard an Atlas-Agena D launch vehicle (serial noted as 353D).

### Q: What happened to the satellite after launch?
A: The satellite reentered the atmosphere on 23 February 1965, marking the end of its orbital mission.

## Why It Matters
Step Thirteen / Plymouth Rock 3 represents a class of small, purpose-built reconnaissance satellites dedicated to signals intelligence. As a 60 kg spacecraft within the P-11 program, it illustrates the U.S. practice of deploying compact SIGINT platforms during the early era of electronic intelligence collection. Its deployment from Vandenberg on an Atlas-Agena D underscores the use of expendable launch systems to place specialized satellites into orbit for relatively short-duration missions. The satellite’s reentry less than a year after launch shows that it was designed for a focused operational window. The combination of a Lockheed-built spacecraft bus with an HRB Systems payload demonstrates a hardware division between platform and sensor/provider roles. As an entry in the P-11 program, Step Thirteen / Plymouth Rock 3 contributes to the historical record of U.S. Air Force-operated reconnaissance efforts and to the technical lineage of small SIGINT satellites.

## Notable For
- Being a small 60 kg dedicated signals intelligence reconnaissance satellite.
- Serving as an element of the U.S. P-11 small satellite SIGINT program.
- Launch aboard an Atlas-Agena D vehicle (serial/identifier 353D) from Vandenberg SLC-4W.
- Having multiple operational and programmatic aliases (e.g., KH 7-13 Capsule, P-11 4302, OPS 5063).
- A clearly documented orbital lifetime ending with atmospheric entry on 1965-02-23.

## Body

### Identification and classification
- Name: Step Thirteen / Plymouth Rock 3.
- Instance of: reconnaissance satellite.
- Use: signals intelligence (SIGINT).
- scn (internal catalog/serial number): 00914.
- COSPAR ID: 1964-068B.
- Country of origin: United States.
- Operator: United States Air Force.
- Part of: P-11 class — an American small satellite SIGINT program.

### Mission and purpose
- Purpose was SIGINT collection as stated in classification and use fields.
- Operated under the U.S. Air Force within the P-11 program framework.
- Designed as a compact reconnaissance platform for electronic/intelligence tasks.

### Launch and orbital history
- Launch date: 1964-10-23 with a time qualifier of 18:27.
- Launch site: Vandenberg Space Launch Complex 4 West.
- Launch vehicle: Atlas-Agena D (identified with qualifier 353D).
- Significant event recorded: rocket launch from Vandenberg SLC-4W on 1964-10-23.
- End of mission: atmospheric entry recorded on 1965-02-23.

### Manufacturer and hardware
- Spacecraft bus manufacturer: Lockheed Corporation.
- Payload manufacturer: HRB Systems.
- The division of applies_to_part indicates Lockheed built the bus and HRB Systems provided the payload instrumentation.

### Physical specifications
- Mass: 60 kilograms.
- No further dimensions or power specifications are provided in the source material.

### Alternate identifiers and program context
- Aliases include: KH 7-13 Capsule; P-11 4302; P11 4302; Mission 7305/7306; OPS 5063; EHH A4.
- Part of the P-11 program, which is classified here as an American small satellite SIGINT program.
- Google Knowledge Graph ID: /g/122qgnzw.
- Wikipedia language entry noted: Polish (pl).

### Significant dates
- Launch: 1964-10-23 (launch time qualifier 18:27).
- Atmospheric entry (reentry): 1965-02-23.

(End of entry.)

## References

1. [Source](https://space.skyrocket.de/doc_sdat/step-13-plymouth-rock-3.htm)
2. Jonathan's Space Report
3. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1964-068B)
4. [Source](https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-068B)