December 15 – Discovery of Saturn’s Moon, Janus (1966)

J R Hind discovered today’s main belt asteroid, 23 Thalia, from Hyde Park, London, on December 15th, 1852 (I’d like to see him try that nowadays). Thalia is an S-type asteroid of about 107 km diameter, located between the 3:1 and 5:2 Kirkwood gaps.

In Greek mythology, Thalia, daughter of Zeus and Mnemosyne, with a name derived from the verb “to flourish”, was the muse of comedy and pastoral poetry. She may or may not (depending on which source you believe) have been the mother of the Corybantes, attendants to the Great Mother of the Gods, and associated with particularly orgiastic rites.

We also have a moon today.  The discovery of Janus, one of the inner Saturnian satellites, is attributed to Audouin Dollfus, who first observed it on December 15th 1966. Three days later, Richard Walker also observed an object in the right place but at the wrong time, which caused confusion for a while, but was eventually found to be another moon, Epimetheus, which shares an orbit with Janus.

Janus, photographed by the Cassini probe (image credit: NASA / JPL / SSI)
Janus, photographed by the Cassini probe (image credit: NASA / JPL / SSI)

Janus is the two-faced Roman god of beginnings, entrances, gates, etc. You should thank him the next time an automatic door opens for you. Janus is also one of the select group of deities after whom a month (January) is named, and strangely he has no Greek counterpart.

1965  –  launch of San Marco 1 by Italy. Being their first satellite, the Italians wisely did not fill it with lots of expensive equipment. It did, though, contain a couple of experiments to study the ionosphere, the layer of the atmosphere stretching from about 60 km to 1,000 km, a region you need to know about if you’re planning to become a space-faring nation, needing to send radio messages over great distances.

2000  –  Death of George Alcock, aged 88, hunter of novae and comets. I believe he found five of each (remarkable for south-eastern England), some of them from indoors using binoculars, and even occasionally through double glazing1!  His eyesight must have been unbelievable.

2014  –  Voyager 1 crossed the termination shock.


2015  –  Launch of Expedition 46 to the International Space Station.  This caused considerable press interest in my homeland (in fact I’m going to call it a frenzy) because in addition to Russian cosmonaut Yuri Malenchenko and American astronaut Tim Kopra, the three-man crew contained Tim Peake, the first Briton to float into the ISS (I was going to say “set foot aboard” the ISS, but I’ve seen the footage, and feet don’t feature much).  Because of the  numbering system they use at the ISS when crews overlap, these three also formed part of Expedition 47.

ISS Expedition 46 Patch
ISS Expedition 46 Patch

As a supporter of Port Vale FC, I was distraught to discover that one of Tim Peake’s tasks whilst on this mission was to unveil a flag featuring the name of our local rivals, Stoke City.  I’ve gone off him a little.


1   Journal of the British Astronomical Association, vol.111, no.2, p.64-66

December 02 – Launch of SOHO (1995)

Built in Europe, the Solar and Heliospheric Observatory (SOHO) was launched on December 2nd, 1995 and, despite being planned as a two year mission, it is still going, with the latest predicted end date being in 2020. It is a joint project between ESA and NASA, built by Matra Marco I Aerospace, and designed to provide data to help predict solar weather, and answer questions about the solar interior, solar wind, and why the corona is so hellishly hot. The mission has been a great success, providing significant insights into such areas as the structure of sunspots, the flow of gases inside the Sun, and the dynamics of the solar wind.

Prominence spotted by SOHO (image: ESA / NASA)
Prominence spotted by SOHO (image: ESA / NASA)

In addition to all this, SOHO has still found time to become history’s greatest ever discoverer of comets, with the total ticking over to an astonishing 3000 on September 13th 2015. Comet number 3000 was spotted by Thai astronomer Worachate Boonplod, part of an amateur army of spotters who betwen them have been responsible for the majority of SOHO discoveries.

The Broad Band X-ray Telescope (BBXRT) was launched today (1990) on board shuttle Columbia flight STS-35. It formed part of the partly-successful “ASTRO-1” payload of four instruments.

In-flight view of BBXRT (image: NASA)
In-flight view of BBXRT (image: NASA)

The mission was somewhat shorter than the previously-mentioned SOHO, as the telescope was attached to the shuttle, and had to go wherever it went (back to Earth).

November 11 – Philae Lands on Comet 67P/C-G

2015Four years years ago today ESA successfully landed (or bounced) their Philae lander on comet 67P/Churyumov–Gerasimenko, having been launched from the Rosetta spacecraft some hours earlier.

The Philae Lander viewed from Rosetta, a few hours into the flight to Comet 67P. (Image credit: ESA)

Rosetta had been launched from French Guiana in 2004, and a soft landing on the target comet was going to be the highlight of the trip. One of Philae’s thrusters was known to be faulty before separation from Rosetta, but there wasn’t much that could be done about it so they went ahead anyway. Earlier I said that Philae “bounced” onto 67P, which I think needs a little more information. There isn’t much gravity on a comet; so if you bounce, you’ll bounce high. Philae bounced just over half a mile (1 km) before coming down again. It was a whisker away from not coming back down and carrying on into space.

Fortunately, despite landing at a jaunty angle and in an unfavourable location, Philae was able to deploy some of the experiments on board, and was capable of several periods of communication with ground controllers via Rosetta.

November 09 – Launch of Venus Express (2005)

Venus Express was the first mission to Venus by the European Space Agency.  It used the same basic platform used for the Mars Express mission of 2003, keeping costs down, and allowing rather a swifter progression than normal from the proposal of the mission to the actual launch.

The launch, on November 9th 2005, was from the Baikonur Cosmodrome, which by that time was no longer behind the Iron Curtain, and available to rent.  I’m not sure how much it costs to launch from Baikonur, but the Russians were paying the Kazakh government $115m (US) a year for the privilege in 2016.

After a voyage of just over 5 months, Venus Express parked in a near-polar orbit, chosen to give it the best view possible of most of the planet.  Obviously most of the focus was on studying the structure and composition of the extremely thick Venusian atmosphere, but observations of the surface have also been made possible by use of the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS).  This has helped support the theory that Venus has recently seen volcanic activity.

Venus Express (image copyright ESA)
Venus Express (image copyright ESA)

You can see VIRTIS on the above image.  Also indicated are the magnetometer (MAG), the Fourier spectrometer (PFS) and the camera (VMC).

After a fairly lengthy working life of nine years (seven more than the original plan) ESA announced the Venus Express mission was over in December 2014.

October 17 – Launch of INTEGRAL (2002)

The International Gamma Ray Astrophysics Physics Laboratory (INTEGRAL) was launched on this day in 2002 by the European Space Agency. 2002 was quite a while ago in spacecraft life-spans, but INTEGRAL is still going strong, and still producing plenty of results.  The launch was provided by the Russian state-owned Roscosmos corporation, and took place at the Baikonur Cosmodrome, using a Proton-K rocket.

Artist’s Impression of INTEGRAL (image: ESA–Medialab)

Highlights of the mission so far have included:

  • observing, in conjunction with the Fermi and Swift space observatories, gamma ray jets near a supermassive black hole using gravitational microlensing;
  • taking part in a multi-observatory study of blazar TXS 0506+056, an active galactic nucleus, and a source of high energy neutrinos;
  • collecting data on the unusual behaviour of the black hole of V404 Cygni during its 2015 outburst;
  • studying “AT2018cow”, the brightest stellar explosion ever recorded, and possibly the birth of a black hole or neutron star.


September 27 – Launch of SMART 1 (2003)

2003  —  Launch of SMART 1 (Small Missions for Advanced Research in Technology) by ESA.  SMART 1 was the first ESA probe to the Moon, and set a couple of unusual records.  It became the first mission to leave Earth orbit using just solar power, and the slowest ever to the Moon, taking 13 months.  It also holds the record for the lowest fuel consumption on an Earth to Moon journey.  As well as testing new power sources, SMART 1 did carry imaging equipment, and identified this location . . . .

Shackleton Crater viewed by SMART 1 (image credit: ESA)

. . . . as the best place to site solar panels for a future lunar base.

June 02 – Launch of Mars Express

Mars Express, launched on this day in 2003, was the first visit to another planet by the European Space Agency (ESA). And, unlike many of the modern long-range voyagers mentioned in these pages, the name “Express” is there to denote speed; it is not a highly-convoluted acronym describing the mission.

Artist’s impression of Mars Explorer. (Credit: Spacecraft: ESA/ATG medialab; Mars: ESA/DLR/FU Berlin)

The journey to Mars began at the Baikonur Cosmodrome and ended six months and 23 days later in orbit around the red planet. With seven instruments on board, Mars Express was able to study just about all physical aspects of its new home, including geology, mineralogy and atmosphere.

Highlights of the mission have included the discovery of minerals which only form in the presence of liquid water, radar detection of subsurface water ice, the possible detection of methane in the atmosphere, and evidence for an ancient system of underground lakes.

Another impressive result was how close Mars Express managed to get to the larger of Mars’ two moons, Phobos. The image below was taken from 351 km, but closest approach was 67 km.

Phobos, photographed by Mars Express. (Image Credit: ESA/DLR/FU Berlin).

The Mars Express orbiter is still going strong, and is expected to remain in service until 2022. Which is more than can be said for the British component of the package, the Beagle 2 lander, which landed on the surface in an impact crater called Isidis Planitia on December 25th 2003, and was never heard from again. More than a decade later a camera on board NASA’s Mars Reconnaissance Orbiter spotted Beagle 2, and close inspection suggested that not all of Beagle’s solar panels deployed successfully.

Image from the HiRISE camera, interpreted as the missing British Beagle 2 lander. (Image credit as in photo).

There’s plenty more to read about this mission at the ESA Mars Express website.


1967 — The unmanned US probe Surveyor 1 landed on the Moon.

1998 — Launch of space shuttle Discovery mission STS-91, carrying the prototype AMS-01, the first of two Alpha Magnetic Spectrometer missions.