SOLRAD 7B (COSPAR ID: 1965-016D)

SOLRAD 7B (COSPAR ID: 1965-016D)
Frequencies	136.8 Hz,136.806 MHz
Frequency Range	136 Hz - 136.806 MHz
Mode	USB
Modulation	AM IRIG
ACF	—
Emission Designator	—
Bandwidth	6 kHz
Location
Short Description	SOLRAD-7B is one of the many "zombie satellites" in orbit and is an artifact of the mid 1960's US space program. It occasionally will become active again when illuminated by sunlight due to the satellite bus having several small, semi-circular solar panels.
I/Q Raw Recording	Download file
Audio Sample

SOLRAD-7B (NORAD ID: 1291) is one of the 10 satellites of it's type that reached orbit. The SOLRAD series was created to measure radiation as a result of solar activity in space, and to help determine what was needed to protect both humans and spacecraft, while also being utilized by NRO under the cover name GRAB (Galactic Radiation and Background) to record the transmitted wavelength of Soviet anti-aircraft radar sites to optimize bomber flight paths during the cold war. It is a roughly 1 foot, spherical satellite carrying several small solar panels with 2 antennas on either side. When it gains enough power from the sun, it will begin transmitting a relatively strong center carrier as well as weak sidebands that are likely where modulated data should be.

"The telemetry is a multiplex of six IRIG-106 7.5% bandwidth sub carrier oscillators, linearly added and amplitude modulate the RFRadio Frequency carrier. IRIG 3 (730 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). centre frequency) and IRIG 4 (960 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). cf) vary in step over 3.6 second with 8 periods of 450 millisecond each. IRIG 5 (1300 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). cf), IRIG 6 (1700 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). cf) and IRIG 7 (2300 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). cf) are all fixed at their lower deviation limit of 1202 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz)., 1572 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). and 2127 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). respectively. IRIG 8 (3000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).) drifts from the the lower limit, 2775 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz)., to the upper limit, 3225 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz)., over time." - from Mike Kenny's site.

On Sunday May 31st, 2026, at around 1:15 PM EST, SOLRAD 7B was observed to be partially modulating data onto several of its subcarriers for around 15-20 seconds.

In comparison to period audio recordings from the "Sounds from Space 1962-1966" segment at the website of Mattias Bopp, this appears to represent that the telemetry system is still partially functional - albeit missing parts from other segments of the system that are still only carrier tones. Observations like this one from SatNOGS show similar activity on these carriers.