Sky & Telescope - January 2025 - 9

SPACE & SOCIETY
First of " Thousand Sails " Fly
A CHINESE COMPANY, Shanghai
Spacecom Satellite Technology, has
launched the first 18 spacecraft of the
megaconstellation named Qianfan
( " Thousand Sails " in Chinese), which
will ultimately include more than
10,000 communications satellites in
low-Earth orbit. Their altitudes, near
800 kilometers (500 miles), are above
those of SpaceX's Starlink satellites,
which are at 500 km, and below those
of Eutelsat's OneWeb constellation at
1,200 km (S&T: June 2021, p. 16).
Several observers saw the satellites
as well as debris from the Long March
6A rocket, which broke apart after
delivering its cargo into orbit. Experienced
visual satellite observers began
recording the satellites' brightness once
the ephemeris data became available.
Observations from Richard Cole, Bram
Dorreman, Scott Harrington and myself
suggest that near zenith the satellites
have a brightness of about magnitude 4.
In the U.S., SpaceX is working with
astronomers to address the problem
of bright spacecraft, and Starlink has
succeeded in significantly reducing the
brightness of its satellites. There are,
however, no regulations in place as yet
that govern satellite brightness. The
Thousand Sails spacecraft at their current
brightness would seriously interfere
Meteorite impacts and volcanic eruptions
can both produce glass beads on the Moon.
ery that points to eruptions within the
past 50 to 100 million years (S&T: Jan.
2015, p. 14). Likewise, centuries of
visual observations of transient lunar
phenomena (TLP) have sometimes been
attributed to volcanism.
Benjamin Weiss (MIT), who was
not involved in the study, says " it
would suggest that the Moon has
been volcanically active essentially
yesterday. " However, given the small
sample size, he would like to see more
examples with similar properties. That
may yet happen, if these methods are
Impact glass beads produced by
a meteorite impact
applied to the more abundant samples
brought back by Apollo astronauts.
These findings are " part of this
growing awareness, " Weiss suggests,
Observatory (NRAO) and SpaceX first
entered an agreement to coordinate
data in 2019. Now, they've developed
an autonomous system that will inform
satellites about the telescope's current
operations, including in which direction
of sky the telescope is pointing and the
radio frequency at which it's observing.
Satellites flying near that region can
then either briefly redirect their transmission
or shut it down altogether to
avoid interference. Scientists have tested
this technique in two separate experiments
using the Green Bank Telescope
An artist's illustration shows bright satellites
on orbits that crisscross the sky.
with astronomical research as well as
aesthetic appreciation of the night sky.
¢ANTHONY MALLAMA
SPACE & SOCIETY
Astronomers and Starlink
Partner for Quieter Radio Sky
STARLINK IS INFAMOUS in astronomy
for its satellites' unwanted brightness,
but the satellite constellation disrupts
high-quality radio observations, too.
Now, radio astronomers and Starlink
engineers have developed a technique
to help prevent the satellites' radio
transmissions from adversely affecting
astronomical observations.
The U.S. National Science Foundation's
National Radio Astronomy
Impact
glass beads
Volcanic
glass beads
and have demonstrated its feasibility.
" My immediate reaction is that this
is a significant step in the right direction, "
says Federico Di Vruno (Square
Kilometre Array Observatory). " The
NRAO team and SpaceX have proven
that beam avoidance is implementable
and that it has a noticeable impact. "
For now, Starlink's agreement
involves only NRAO facilities; however,
SpaceX is in discussions with other
observatories to expand implementation.
For it to be truly effective, other
satellite companies and governments
will need to adopt it as well.
Even with this system, though, some
science will require longer observations
and more aggressive " cleaning " of radio
data to root out artificial noise. Unintentional
transmissions from satellite
electronics also remain an issue.
¢JURE JAPELJ
Glass beads produced by
a volcanic eruption
" that maybe the Moon had this longer
and more protracted history of geologic
activity. "
¢DAVID L. CHANDLER
sk yand tele scope .o r g * JANUARY 2025
9
SATELLITE ILLUSTRATION: LEAH TISCIONE / S&T; GLASS BEADS: T. ZHANG & Y. WANG
http://skyandtelescope.org
Sky & Telescope - January 2025

Table of Contents for the Digital Edition of Sky & Telescope - January 2025
