EXPLORER 38 (RAE-A)

About This Satellite

Explorer 38, known as RAE-A or RAE-1, was launched in July 1968 to investigate long-wavelength radio emission. Its targets included the solar corona, the Galaxy, and phenomena in Earth's magnetosphere. It was a radio observatory, not an optical camera: its receivers measured signals that would not appear as a conventional photograph of the sky.

The antennas were a major part of the observatory

The instrument paper describes two 229-metre antennas and radiometer systems spanning 0.2 to 9.2 MHz. Supporting equipment included antenna-impedance probes and television cameras for monitoring antenna shape. Those cameras served the experiment's engineering needs; their presence does not turn RAE-1 into a television imaging survey of astronomical objects.

Knowing the antenna mattered to knowing the sky

The paper discusses experiment design, calibration, and performance together. A received radio level cannot be interpreted independently of the antenna and receiver response. The exceptionally large antenna structures and their monitoring equipment were therefore parts of the measurement system, not merely decorative appendages to a small satellite body.

Mission reference: NASA NTRS: RAE-1 low-frequency observatory design and performance. Editorial review: 2026-09-14.

Signals from below could compete with signals from space

A study using RAE-1 observations compared the two antenna views to distinguish radiation arriving from above from terrestrial interference below. It identified interference associated with thunderstorms and groups of ground-based transmitters, alongside solar bursts. Being in orbit did not automatically give the instrument a radio-quiet environment or make every detected burst astronomical.

Reference: NASA NTRS: RAE-1 radio observations, terrestrial interference and data selection.

Selecting the data was part of the scientific result

That analysis used the V-antenna radiometer data, rather than every detection system aboard the satellite. The authors describe preliminary inspection of microfilm records and intervals with little terrestrial interference. To interpret a reported result, identify the receiver, frequency, selection criteria, and observing interval; the satellite's orbit alone cannot establish which measurements entered the analysis.

Reference: NASA NTRS: receiver selection and screening of RAE-1 observations.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-04. Estimated altitude ranges from 5,825 km at perigee to 5,861 km at apogee, a difference of 35 km. The orbital period is about 224.1 minutes. Eccentricity 0.00145 indicates a nearly circular path. In a two-body approximation, perigee speed is 1.00 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 120.82 degrees implies approximate geocentric ground-track limits of 59.2 degrees north and south. This is a retrograde orbit, moving against the direction of 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 3307 · GCAT: S03307 (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)

Satellite Details