  We report on observations of 68 satellites belonging to the SpaceX Starlink
constellation with the LOFAR radio telescope. Radiation associated with
Starlink satellites was detected at observing frequencies between 110 and 188
MHz. A combination of broad-band features, covering the entire observed
bandwidth, as well as narrow-band (bandwidth < 12.2 kHz) emission at
frequencies of 125, 135, 143.05, 150, and 175 MHz, was observed. The presence
and properties of both the narrow- and broad-band features vary between
satellites at different orbital altitudes. While the narrow-band detections at
143.05 MHz can be attributed to reflections of radar signals from the French
GRAVES Space Surveillance Radar, the signal properties of the broad- and
narrow-band features at the other frequencies suggest that this radiation is
intrinsic to the Starlink satellites and it is seen for 47 out of the 68
Starlink satellites that were observed. We observed spectral power flux
densities vary from 0.1 to 10 Jy for broad-band radiation, to 10 to 500 Jy for
some of the narrow-band radiation, equivalent to electric field strengths of up
to 49 dB[uV/m] (as measured at a 10 m distance from the satellites, with a
measurement bandwidth of 120 kHz). In addition, we present equivalent power
flux density simulations of the full Starlink phase 1 constellation, as well as
other satellite constellations, for one frequency band allocated to radio
astronomy by the International Telecommunication Union (ITU). With these, we
calculate the maximum radiation level that each satellite constellation would
need to have to comply with regulatory limits for intended emissions in that
band. However, these limits do not apply if the radiation is unintended, that
is to say if it does not originate from intentionally radiated signals for
radio communication or other purposes. (shortened)
