Reports

Mission "Polymele" in Senegal

Aïssata Thiam, PhD candidate in geophysics at UCAD and her teammate, Abdoulaye Sow, are training to assemble the telescope at the Royal Malango Hotel in Fatick.

The occultation of a star by the asteroid Polymele has been observed from Kaolack, Senegal.

During the night of 23rd to 24th September 2020, an international scientific cooperation, mobilising Senegalese, Belgian and French researchers, made it possible to observe for the first time a star occultation by the asteroid (15094) Polymele. This observation campaign is part of the preparations for NASA's Lucy space mission.

Formation of the solar system

Coordinated by NASA, the Lucy space mission will start in October 2021 for 12 years. Its objective: to fly by an asteroid in the main belt and six Trojan asteroids of Jupiter, small rocky bodies that follow (or precede) the planet at a stable distance on the same orbit around the Sun. The aim is to improve our knowledge of the origin of the planets and the formation of the solar system.

A preparatory step for the flyby is for astronomers to determine the size and shape of the asteroids. Since they reflect very little sunlight, direct observation is difficult: measurements are made by observing the shadows they form as they pass in front of a distant star, a phenomenon called stellar occultation.

Second mission

Already in 2018, 50 American, 7 French and 21 Senegalese researchers had observed from Senegal the last occultation of the asteroid Arrokoth, before its overflight in January 2019 by the New Horizons probe. On the strength of this success, Marc Buie of the Southwest Research Institute, who is contributing to the preparation of the Lucy mission, convinced NASA to entrust a new mission to the Senegalese Association for the Promotion of Astronomy (ASPA).

Senegal was indeed, according to forecasts, ideally placed for the observation of the occultation of a star by (15094) Polymele, the smallest of the six Trojan asteroids, which will be flown by the Lucy mission in 2027. The data collected would be used to learn more about the asteroid before launching the probe.

Intensive training

On the night of 23rd to 24th September, the international team assembled in Senegal effectively observed this stellar occultation by Polymele. About forty researchers were mobilised, with the support of IRD and CNRS.

Fourteen mobile telescopes measuring 20 centimetres in diameter were deployed at different observation sites in the Fatick and Kaolack regions of Senegal. The intensive training of researchers in the installation and use of these telescopes and their acquisition systems, sent by NASA to Senegal, took place during the three days preceding the occultation at Fatick.

Successful observation

Despite the development of a large storm cell over the Kaolack region on the night of the observation, the deployment strategy of the telescopes proved to be effective in observing the stellar occultation. The data collected will enable a first estimate of the size of the Polymele asteroid to be obtained, while the shape of the object will be specified by future observation campaigns.

This successful observation campaign, carried out overwhelmingly by Senegalese astronomers, marks an important step in the development of astronomical research in Senegal. These actions illustrate a coordinated effort to promote astronomical and space sciences in Africa, led since 2017 by an international consortium of researchers: the African Planet and Space Science Initiative.

Watch more about the preparation and training of the teams before the observation in this slideshow.

The star occulted by the asteroid Polymele is marked in red. Since the telescope was partly manually pointed in its direction, the observers had to learn how to spot this part of the sky with their own eyes.
The hardware needed for the observations (nearly two metric tons) is loaded into the IRD's nine 4x4 SUVs at the agency's delegation headquarters in Dakar, to be conveyed to the operations headquarters in Fatick.
The hardware needed for the observations (nearly two metric tons) is loaded into the IRD's nine 4x4 SUVs at the agency's delegation headquarters in Dakar, to be conveyed to the operations headquarters in Fatick.
The hardware needed for the observations (nearly two metric tons) is loaded into the IRD's nine 4x4 SUVs at the agency's delegation headquarters in Dakar, to be conveyed to the operations headquarters in Fatick.
Aissata Thiam, a PhD student at UCAD, shows how to assemble the telescope after watching a training video, under the supervision of Sylvain Bouley who comments on the operation for the training of all the participants. This assembly operation is repeated several times so that it can then be carried out without difficulty on the observation site, at night, in more stressful conditions, and within a limited time.
The coordinates of the observation site are entered on the control pad, which is part of the alignment procedure that allows the telescope to compensate for the Earth's motion and to follow the stars during the observation.
Cheikh Ahmadou Bamba Niang, the first PhD student in planetology at UCAD, has just finished assembling his telescope.
Riad Kawar and Dembo Diakhité, who form one of the 14 observation teams, are training together to set up the telescope. Each team is composed of two Senegalese researchers who will be responsible for all phases of telescope assembly, adjustment and data acquisition during the night of the observation.
Aïssata Thiam, a PhD candidate in geophysics at UCAD, and her teammate, Abdoulaye Sow, practice assembling the telescope at the Royal Malango Hotel in Fatick.
The teams meet every day to assemble and disassemble the equipment several times on the grounds of the Royal Malango Hotel in Fatick, in order to be ready for the night of the occultation.
Together with David Baratoux from IRD, Makhoudia Fall and his teammate Omar Marigo check the movements of the telescope with the control pad, during a training session on the grounds of the Royal Malango Hotel in Fatick.
Training session on the grounds of the Royal Malango Hotel in Fatick.
Training session on the grounds of the Royal Malango Hotel in Fatick.
Training session on the grounds of the Royal Malango Hotel in Fatick.
The four women of the |dq|Polymele|dq| team, Katrien Kolenberg, from the University of Antwerp, Marame Ngom, Aissata Thiam, and Ihmal Loubane, from UCAD, with Baidy Demba Diop, from the Senegalese Association for the Promotion of Astronomy.
Part of the |dq|Polymele|dq| team.
After the observation, the equipment is checked at the IRD representation in Dakar, before being sent back to the United States.
Maram Kaire, coordinator of the mission (centre) with David Baratoux, coordinator of the Franco-Belgian team (foreground)

The video of the Polymele occultation, observed in Senegal on 24th September 2020, shows the brevity of the phenomenon, and the performance achieved by the researchers.

 

This article comes form a release published by IRD. It has been translated and adapted by Afriscitech.

About

Afriscitech, all science throughout all Africa.

Follow the news about scientific and technological research in Africa and by Africans.

 

Who are we?

Afriscitech.com is published by Coopetic.

- Luc Allemand, Editor in Chief

Cookies settings

×

Functional Cookies

This site uses cookies to ensure its proper functioning, which cannot be disabled from our systems. We do not use them for advertising purposes. If these cookies are blocked, some parts of the site will not work.

Measure of audience

This website uses cookies to measure and analyse audiences, such as Google Analytics and Google Ads, in order to evaluate and improve our website.

Interactive Content

This site uses third-party components, such as ReCAPTCHA, Google Maps, MailChimp or Calameo, which may store cookies on your machine. If you decide to block a component, the content will not be displayed

Social Networks / Videos

Social network and video plug-ins, which use cookies, are available on this website. They make it possible to improve the user-friendliness and promotion of the site through various social interactions.

Other cookies

This Joomla CMS uses a number of cookies to manage user sessions, for example.

Search