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EXPLORER 20, 870

Orbit data source: Space-Track

EXPLORER 20, 870 is a payload satellite owned by GSFC (US) in LEO that was launched on Tue, 25 Aug 1964 UTC via an SCOUT X-4 launch vehicle from the Air Force Western Test Range (AFWTR). Payload-class satellites include a variety of spacecraft equipped with specific instruments for various scientific and technological missions. These include communications satellites like Starlink; space stations such as the ISS; scientific satellites like the Hubble; Earth observation satellites from companies like Planet Labs, Umbra, and HawkEye 360; GPS; miniature CubeSats for education and research; and military/defense satellites.

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<iframe src="https://www.satcat.com/sats-embedded/870?theme=dark&initialShowStats=false" width="600" height="400" frameborder="0" title="Kayhan Space Satcat Satellite Viewer"></iframe>

Iframe URL

https://www.satcat.com/sats-embedded/870?theme=dark&initialShowStats=false

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ISO8601 Format

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ISO8601 Format

Identifier

870, 1964-051A

Orbit

LEO

Country

Related business

National Aeronautics and Space Administration (NASA) (US)

Manufacturer

Cutler-Hammer/AIL

Mission

Civil Science

Bus & Motor

S-48, Unknown motor

Mass

44 kg wet, 44 kg dry

Launch date (UTC)

1964-08-25 (61 years ago)

Launch vehicle

SCOUT X-4

Launch site

Air Force Western Test Range (AFWTR)

Object type

Payload

Rocket body

Debris

Shape & HBR

Double Cone + 6 Rod, 18.5 m

Radar Cross Section

0.292 m², Medium (>0.1 m² and < 1m²)

Expand to show TLE details & history
Last TLE update: 13 hours ago

TLE from 13 hours ago

0 EXPLORER 20
1 00870U 64051A   25259.19922718  .00000120  00000-0  86393-4 0  9999
2 00870  79.8978 216.8898 0096241 284.1191  74.9284 13.91711744 95326

Epoch: 2025-09-16T04:46Z

TLE epoch observation values (Epoch: 2025-09-16T04:46:53.228Z)

Latitude

-0.00007°

Longitude

149.77505°

Altitude

907.826 km

Speed

7.407 km/s

True Right ascension

14h 27m 33s

True Declination

0° 00' 00"

Sunlit

Object was in daylight at epoch

Visualization orbit readout

Latitude

Unknown

Longitude

Unknown

Altitude

Unknown

Speed

Unknown

Apparent Right ascension

Unknown

Apparent Declination

Unknown

Sunlit

N/A

Visualization observer readout

Local Sidereal Time

10:39:39

Azimuth

Unknown

Elevation

Unknown

Doppler factor

Unknown

Orbital elements

Apogee altitude

990.142 km

Perigee altitude

849.668 km

Semi-major axis

7,298.042 km

Eccentricity

0.00962

Inclination

79.8978°

RAAN

216.8898°

Arg. of periapsis

284.1191°

True anomaly

75.99658°

Mean anomaly

74.9284°

Eccentric anomaly

75.46216°

Mean motion

3.48124 °/min

Orbital period

103.41 mins

BSTAR

0.000086393

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Other satellites on launch #51 in the year 1964 (1964-08-25 UTC)

SCOUT X-4 R/B, 871

SCOUT X-4 DEB, 873 (Decayed)

SCOUT X-4 DEB, 874 (Decayed)

SCOUT X-4 DEB, 875 (Decayed)

SCOUT X-4 DEB, 40592 (Decayed)

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You can import UDL-sourced sensor .json files into the Sandbox to generate a visibility chart that accounts for multi-vendor sensor geometry.

Click here to try in Sandbox

EXPLORER 20 Visibility forecast

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Span	Click to sort rows by Start time (UTC) header in descending order	Start Az.	Max El. time (UTC)	Max El. Az.	Max El.	End time (UTC)	End Az.
10 mins	2025-09-16 22:09:23.709Z	188.713° SSW	2025-09-16 22:13:23.709Z	183.584° SSW	44.487°	2025-09-16 22:19:23.709Z	11.383° NNE
5 mins	2025-09-17 07:16:23.709Z	41.801° NE	2025-09-17 07:18:23.709Z	62.337° ENE	13.923°	2025-09-17 07:21:23.709Z	91.655° ESE
10 mins	2025-09-17 08:59:23.709Z	348.458° N	2025-09-17 09:03:23.709Z	340.227° N	44.479°	2025-09-17 09:09:23.709Z	171.69° S

Co-orbital & Co-planar RSOs

Thresholds — Semi-major Axis: ±100 km, RAAN: ±3°, Inclination: ±5°
TCA is derived from TLE conjunctions

Please sign-in to view Co-orbital & Co-planar RSOs.

Click to sort rows by RSO header in ascending order	Click to sort rows by Country header in ascending order	Click to sort rows by Type header in ascending order	Click to sort rows by Inclination Δ header in ascending order	Click to sort rows by RAAN Δ header in ascending order	Click to sort rows by Coplanar Angle header in ascending order	Click to sort rows by SMA Δ header in ascending order	Click to sort rows by Orbital period header in ascending order	Click to sort rows by <5km Md TCA header in ascending order

CAUTION: Conjunctions in this section are generated from low-fidelity TLE screenings

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Check out EXPLORER 20, 870 on other resources

View EXPLORER 20, 870 on NASA - NSSDCA Website

View EXPLORER 20, 870 on Heavens-Above

View EXPLORER 20, 870 on Keep Track

View EXPLORER 20, 870 on Celestrak

View EXPLORER 20, 870 on Gunter's Space Page

Satcat and Kayhan Space are not affiliated with NASA, Celestrak, Heavens-Above, Keep Track, or Gunter's Space Page.

EXPLORER 20, 870

Orbit data source: Space-Track

Expand to show TLE details & historyLast TLE update: 13 hours ago

TLE from 13 hours ago

TLE epoch observation values (Epoch: 2025-09-16T04:46:53.228Z)

Visualization orbit readout

Visualization observer readout

Orbital elements

Other satellites on launch #51 in the year 1964 (1964-08-25 UTC)

EXPLORER 20 Visibility forecast

Co-orbital & Co-planar RSOs

Check out EXPLORER 20, 870 on other resources

Documentation

Expand to show TLE details & history
Last TLE update: 13 hours ago