1. Carlos Tapia & Lucía García
My name is Lucía García and I’ll present the Work Package 4 part regarding the Photometers.
TESS-W Photometers

2. TESS-W photometer
The Telescope Encoder and Sky Sensor - WiFi (TESS-W) is a compact device that monitors zenith sky brightness every night
It is designed to be installed permanently outside sending data remotely to a network. (Weatherproof enclosure + WiFi)
Extra features. Anti-condensation heating, cloud detector...
TESS stands for Telescope Encoder and sky Sensor and it is basically a device designed to monitor sky brightness every night and therefore light pollution.
¿Why we needed our own design? Our photometer is to be installed permanently on the outside sending data 24/7 to a network. This is why it is mounted in a weatherproof enclosure and sends the measures trough the WIFI connection.
and it comes along with features such as an anti-condensation heating and a cloud detector.
And all this, is open hardware so all the information is available online including the electronic schematics that can be checked on deliverable 4.7 (pages 8 and 9) so anyone could replicate this design.

3. Open hardware Weatherproof enclosure box Clear glass window
Dichroic filter
Light collector
Light sensor
Custom printed circuit board
Infrared thermometer
Heater
WiFi + microcontroller chip
5V USB power supply with 5m wire
Being open and low cost doesn’t mean a lack of quality. We actually designed a device that takes measures that can be use for scientific purposes and we have already published a paper with the whole description of the device.
We can check the basics, here there is the glass window that allows the light to enter the device, going trough the dichroic filter. All the light is gathered thanks to the light collector and measured by the light sensor.
All the electronics is mounted on a custom printed circuit board. Attached to the up cover you can see the infrared thermometer that allows us to estimate the cloud coverage and the resistant that heats up whenever we want to remove the mist that we could be formed sometimes during the winter.

4. nIR filter sensible beyond red
The detector is sensible to light beyond red. (Black line)
We asked for a custom made filter that is flat and, transmits light from 400 to 750 nm blocking the rest. (Green line)
The response is better than other photometers mainly because is not missing the nIR part. (Green vs blue)
The sensor that we are using detects light on the infrared, as you can see in the up figure shown with a black line on top of the astronomical Johnson bands so we had to add a filter.
We installed a custom made dichroic filter with a very good transmission for the visible light that blocks all the infrared and UV as seen with the green line of the middle figure. The blue line is the transmission of an SQM photometer as reference.
From the combination of both we have the response of the device. That would be the green line of the figure below and as you can see it includes both the light as seen with the naked eye during the day and during the night
Scotopic (dash line) (night) (during the night your eyes are more sensitive to blue light)
CIE photopic (continuous line) (day)
The SQM is designed so it imitates the eye response.
TESS photometer on the other hand measures all the visible light.
FOV TESS-W 18º (You will get a 50% 9º apart from the vertical line)
FOV SQM 20º

5. Calibration process at optical lab
We are calibrating the photometer on an optical laboratory. Here you can see some of the photometers in the process of being test.
This is an integrating sphere, a device that allows you to have a uniform light in all directions.
There is a master photometer to perform cross calibration with every device so we can assign a correspondent zero point to all of them. This makes we able to compare the measures all around the world compensating the slight differences that collectors or sensors may have.
Anyway the difference between zero points are always below 10%.
Photo credit: Carlos Tapia

6. Cross calibrated Calibration under real sky
Comparing with ASTMON and SAND
TESS photometer has not only being tested on the lab, but also under a real sky. This picture was taken in our astronomy observatory, you can see the cupolas at the back. So we could cross the measurements between them and with the ones taken by other instruments such as ASTMON and SAND.
How does crossed calibration between 2 photometers look like?
¿Añado la foto de Antonio?
Comprobar si se dice cross calibration o crossed calibration.
Photo credit: Carlos Tapia

7. stars2 & stars5 cross calibration
Madrid
Observatorio
UCM
Villaverde del Ducado
(Mind the moon effect)
Well… just like this.
This is one year of data took by two photometers. Color indicates brightness being dark violet the darker and light blue the brightest.
The first figure was taken by a photometer installed in our observatory in Madrid city center so it took pretty bright measures, indicated by the red and light violet colors.
The one below represents the data acquired by another photometer that was set up in a darker location, as you can see from the predominant navy blue color. It is a small village called Villaverde del Ducado in Guadalajara and it’s interesting to notice that the red vertical lines correspond to the full moon while this effect cannot be observed in Madrid as it is highly polluted.
Comprobar si se dice cross calibration o crossed calibration.
stars2 & stars5 cross calibration

8. Deployed network
Extending currently existing professional photometer networks.
Destinations: Researchers, observatories, cities and dark places +
Why we choose those places?
We choose both bright cities and dark locations. We choose relevant people dedicated professionally to light pollution, some astronomical observatories where we could cross calibrate our data with their instruments like (IAA) and places of interest such as national dark parks where we have been able to test that citizens with no previous background are able to set up and produce data.
So we have 42 photometers sending data day and night.
25 more photometers have been sent to different places recently and there are being installed, so we have 67 photometers deployed in total.
We already have 560 GB of data, and mind you that we are collecting just text lines, so, that’s quite an achivement.
REECL Network
TESS Network

9. Local access to the data
First of all the user can check the data locally, not only with the phone as we saw at the beginning but also with a computer and record all your data.
D 4.3 Communication modules (prototype) – Page 7

10. Online access to data
Users can also share their data to our network after a one time set up. The access is completely open and you can find it on Zenodo.

11. Red Española de Estudios de Contaminación Lumínica
Darkness
We have created a draft system to visualize life data online and it already forms part of the “Red Española de Estudios de Contaminación Lumínica”. This is last Friday’s graphic. Darkness increases in vertical and times evolves in horizontal.
This is a way of comparing the sky of different places over the same night getting a low curve in light polluted places and a higher one in dark locations.
As you can see most of the data is concentrated on the central sector as most of the sensors that are shown on the figure are located in Europe although this one over here in turquoise color is located in Tucson, Arizona, and as you could appreciate the night night happens to be a few hours later.
¿Puedo decir que esto lo hemos hecho nosotros sin problema?

12. Thank you
Comparar con el final report por si hemos comentado algo que no hayamos dicho aquí.