Hunga Tonga volcano eruption

Following an intense period with significant volcanic activity, a large eruption of Hunga Tonga volcano occurred on 15 of January 2022 at around 4:15GMT. The violent eruption sent clouds of ashes 17km into atmosphere and created a large tsunami which affected regions as far as Peru.

        The following article is intended to offer a small analysis of the eruption using remote sensing technologies as well as some introductory elements about the orbits of the satellite which captured the images.

        The images were captured using GOES West satellite, operated by NOAA with the supervision of NASA. The satellite monitors West Pacific region and, because of its geosynchronous orbit, was able to perfectly catch the eruption.  Below you can see the moment of eruption using geocolor, a multispectral composition (composed form 2 visible bands for daytime and 2 infrared bans for night time) which almost reproduce the image viewed by human eyes from space.

Eruption happens at 20° S 175° W and it leads to a circle of ashes with 500km in diameter

        Because of its meteorological research goal, the satellite is equipped with numerous scientific instruments able to better capture the phenomenon. Advanced Baseline Imager is the main instrument of the spacecraft, able to capture 16 spectral bands (2 visible, 4 near IR, 10 IR) in a nadir-pointing orientation.

        Captures form below, on the left side, show the eruption using an Infrared band with 11.2 μm wavelength which was designed for better analyzing cloud formation. As we can see, a big, 500 km wide, ash cloud was formed immediately after the eruption, completely blotting out the sun. On the right side, the phenomenon is shown using AirMass RGB Compound which was designed for airmasses monitoring. The pressure shock wave, visible in the capture could be measured with specific instruments as far as Norway.

IR spectrum (Band 14)

AirMass RGB

        Another effect of the eruption was a abnormally intense lightning activity which was captured using Geostationary Lightning Mapper instrument, but it is not covered by this article.

        The reason why GOES-17 satellite was able to perfectly capture the Hunga Tonga eruption was because it operates in a geosynchronous  equatorial orbit, meaning that the spacecraft will stat at the same point relative to the Earth, appearing motionless to a ground observer. This kind of orbits has its orbital period equal to Earth's rotational period and it is situated at an altitude of 35,786 km above the Equator.

Hohmann transfer orbit using GMAT

        In order to achieve such orbits it is necessary firstly to put the spacecraft on a temporary low-Earth parking orbit and then perform two firing maneuvers, one for entering the transfer orbit and one to exit it. This operation is called a Hohmann Transfer orbit and it has the main advantage that it use the minimum amount of fuel for orbit change.

        The above simulation was created using General Mission Analysis Tool and it consists in two velocity-direction maneuvers, one for rising the spacecraft altitude and one to circularize it as explained above.

Thanks for reading!