EXPLORER 7

About This Satellite

Explorer 7 carried an early experiment to investigate the radiation exchanged by Earth and its surroundings. Instead of taking ordinary cloud photographs, its thermal-radiation package used five bolometers. This made the mission part of the effort to understand the energy driving the Earth-atmosphere system.

Different coatings helped separate different radiation

The experiment used sensor surfaces with different responses to incoming radiation and measured their temperatures with thermistors. Comparing those responses helped distinguish radiation components. A sensor temperature is an intermediate measurement; it is not simply the temperature of the ground directly underneath the satellite.

One instrument, more than one archive product

Before downloading an Explorer 7 dataset, check which sensor, illumination condition, and dates it includes. A selected nighttime product is not a complete record of all experiments or all mission days. This distinction is especially important when trying to compare the archive with a modern radiation dataset.

Mission reference: NASA experiment catalog: Explorer 7 thermal radiation. Editorial review: 2026-09-12.

A restored dataset with a narrower time span

NASA archives a white-sensor nighttime temperature product covering November 15, 1959 to May 24, 1960, with radiance and geolocation information. Its description dates the launch to October 13, 1959. The product was restored in its original IBM EBCDIC text format, so reading it requires attention to encoding as well as scientific units.

Reference: NASA GES DISC: Explorer 7 restored nighttime data.

Thermal radiation was not the only investigation

A published Explorer 7 study used a shielded Geiger tube to examine cosmic-ray intensity by latitude between October 1959 and February 1961. That is a particle measurement, distinct from the bolometer experiment. Combining both under the word radiation should not imply that they measure the same physical quantity.

Reference: NASA NTRS: Explorer 7 cosmic-ray latitude survey.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-04. Estimated altitude ranges from 423 km at perigee to 525 km at apogee, a difference of 102 km. The orbital period is about 94.1 minutes. Eccentricity 0.00744 indicates a nearly circular path. In a two-body approximation, perigee speed is 1.01 times apogee speed. These are mean-element estimates, not instantaneous measurements. Distance per orbit uses an ellipse approximation.

Saved build snapshot. If a valid TLE is retrieved, this explanation and the orbit panel update together. Otherwise this dated snapshot is retained.

Ground track is not sensor coverage

An inclination of 50.24 degrees implies approximate geocentric ground-track limits of 50.2 degrees north and south. This is a prograde orbit, moving in the same general direction as Earth rotation. The plotted line marks the point beneath the object. It does not represent camera coverage, radio reception, or a guaranteed visible pass.

Accuracy and missing information

The introductory record describes the build snapshot. The orbital snapshot explanation and orbit panel share any successfully retrieved TLE; check the displayed epoch. Reentered objects retain historical data only. Mission history is not rewritten by TLE updates. TLE/SGP4 positions are predictions and can change after maneuvers or updated observations. The 14-day stale-data cutoff is a display safeguard, not an accuracy guarantee. Local passes are geometric predictions, not a visibility forecast. No verified operator or mission status means unknown, not active. Do not use this catalog for collision avoidance or operational flight decisions.

Catalog sources: CelesTrak SATCAT: NORAD 22 · GCAT: S00022 (source update 2026 Sep 4 2345:57). Supplementary metadata: SatNOGS DB, retrieved 2026-09-05T12:57:25.375Z. Page assembled 2026-09-15. GCAT phase codes describe trajectory phases, not mission health.

Learn more: TLE data · Perigee and apogee · Ground tracks · JOT (Jewawud Live Orbital Map)

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