Constellations of satellites for Optical Earth Observations

Being able to access maps of any part of the globe updated on daily basis whenever necessary could have important benefits for scientific reason as well as for better emergencies evaluations.

Constellations can avoid one of the most common problems with Earth Optical Observations from satellite. Clouds covering a region and blocking the view. If there’s one single satellite that passes over a region every 30 days and there’s a cloudy day it may be necessary to wait till next time the satellite will be above the same region, 30 days later. Doubling the observation time for many applications is not acceptable.

Most of the time different satellite operators, from different countries, may share data solving the problem, perhaps with only some days of delay.

Why is the update frequency of the maps important?

Agricultural improvements. Instead of receiving data once each month, being able to access information everyday on crops and soil condition that may allow farmers to deal with droughts more efficiently increasing the overall productivity.

Emergencies like earthquakes, floods, forest fires, humanitarian crisis etc. All these need rapid information in order to coordinate the emergency teams more efficiently. For example in case of earthquakes or floods it could be possible to identify places with major damage or obstacles that could slow emergency teams.

Planet Labs is a company that works with a constellation of optical satellites (Doves) many about 10x10x30 cm in size. They manage to create maps of the whole globe updated on daily basis. Gallery of some of their photos from space.


Trappist-1 and the 7 Earth-Size planets

The discovery of 7 Earth-Size planets by Nasa has been very popular. Let’s see some key aspects of this star and its planets.

Trappist-1: red dwarf with a mass equal to 8% of the solar mass. Just above the limit for nuclear fusion to be possible.

7 planets: Orbital period from 1.51 to maximum 20 days. Distance from star is about 3% Earth distance from Sun. Planet radius between 0.76 and 1.13 Earth’s radius.

This chart shows, on the top row, artist conceptions of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii and masses as compared to those of Earth. The bottom row shows data about Mercury, Venus, Earth and Mars.

As we can see the 7 planets are Earth-Size planets but besides that the system itself is very different from our own. This could mean it had a completely different evolutionary process.

Planets the size of Earth do not guarantee the necessary conditions for life to develop even if situated in the habitable zone of the solar system. A planetary magnetic field is required in order to have an atmosphere. Latest discoveries have proved how Mars lost its atmosphere because of the solar wind that slowly ripped away the molecules.

Even if the Trappist-1 is smaller then the Sun the planets are much closer then Earth. Star radiation could be a problem and other negative aspects due to this proximity could also be present.

Life needs challenges that force it to evolve, an unstable environment. Systems that are too stable don’t create the necessary conditions for life to evolve. Too unstable ones destroy the elementary life forms.

So why should someone do these researches? Models built to describe how the Solar System has formed need to be verified. Similar stellar system at different evolutionary stages could help understand what happened and what will happen to our system.

Trappist-1 is about 39.5 light year away. The simplest conversation would take about 80 years just for the initial presentations. Finding extraterrestrial life sure is interesting but it’s just the last of the goals.

Drones and satellite observations. Biodiversity and LiDAR.

There are satellites constantly observing every single part of planet Earth. Some of them with a resolution of about a meter, military ones even less. Sometimes they are single objects, other times they form constellations. ESA Copernicus Program is based on a constellation of satellites called Sentinels.  

FA (TS Author)
Considering the price for same images you wonder if a drone cannot do the same or better for less money.

This is a good question, but I imagine drones would have to fly higher than is currently permitted in order to do useful imaging, making them a serious hazard to passenger aviation. As far as I’m concerned, the fewer drones in the sky, the better.

No doubt drones could become dangerous if not used properly. Still following rigorous rules they could become a resource being complementary to satellite data. 

FA (TS Author)
It depends on how vast is the observed area. Drones cannot compete with satellite when it comes to global observations. Still a city or a small agricultural region could be well covered. Since we have helicopters that fly over cities I think drones will be little hazard for civil aviation. Obviously we speak about a few drones per city not millions of them 🙂

Probably. But you have to be physically near your AOI. The municipality where I live does a lot of its urban planning photography from a balloon. I don’t know about the economics of IR sensors, either. I can’t imagine they are cheap or easy to replace if you land your drone in the river.

Particularly drones based on LiDAR (Light Detection and Ranging) technology able to analyse the biodiversity of a region by mapping the distribution of plants in a forest. They are much more then simple IR sensors. Though IR could also provide great information on vegetation.

LiDAR combined with new 3D and autonomous cars diffusion could really become a fantastic combination for the future. You could find many videos on this technology and here I suggest one that may visually explain the concepts in this post.

Continua a leggere

Tesla Motors and the electrical infrastructure

Looking at the electrical cars they came up with, Tesla Motors is doing a great job. Hopefully in the future this kind of technology would eliminate most of the greenhouse gases emissions due to road transportation.

Even if there’s actually a boom of customers for the next Tesla Model 3, a critical problem persists. The infrastructure of electrical charging points. Is there any real infrastructure able to guarantee the access to large number of cars?

Based on what can be found on Tesla Motors website, after charging the batteries for 30 minutes you get:

  • Home 11 kW -27 km
  • Chademo 50 kW – 137 km
  • Supercharger 120 kW -270 km

By improving the power there is a reduction of the recharging time. However even this way if there’s a need to charge the batteries of 10 cars, unless your electric station has a very high available power, it will prove to be quite difficult to do in short time.

So, the real news here is not Tesla launching a new car model. They actually plan to expand their charge stations based on Supercharger technology. This will be part of the infrastructure that will allow and easy expansion of electric cars on the market.

Now… non everyone has 11 kW Home power, and cars still cost a lot. The huge demand of electricity, imagining all cars will be electric,  will bring a rise of prices for electrical power. So there’s still much to be done.