#SocialSpaceWA - ESA's First Western Australian SocialSpace event!

BACKGROUND

When you hear "European Space Agency Deep Space Tracking Station," it's understandable that the first thing you think of is that it's somewhere in Europe. While there is a station located in Europe, the ESA actually has two other deep space antennas equally spaced around the world as part of their Estrack network. Estrack is a global system of ground stations providing links between satellites in orbit and ESOC, the European Space Operations Centre, Darmstadt, Germany.

 Deep Space Antenna 1 (DSA 1) is located in New Norcia, Western Australia. It was commissioned in 2002 and was the first antenna in ESA's Deep Space Network, which was designed to give the ESA an independent  capability to communicate and control deep space missions. It is a huge 35m diameter parabolic dish, with the capability to communicate beyond Mars. The first signals received by this station were from the NASA Stardust mission in June 2002.
DSA 2 is located 77 kms west of Madrid, Spain, at a place called Cebreros. Like DSA 1, the dish in Spain is a 35m diameter. It is separated from DSA 1 by 120 degrees of longitude, and was first commissioned in 2005
DSA 3 is another 120 degrees around the globe, at Malargüe, Argentina. It began operation in 2012.

The three Deep Space Antennas complement the NASA Deep Space Network, giving a combined total of 6 stations. Three in the Northern Hemisphere, and 3 in the Southern Hemisphere.

Estrack have a number of other resources in Western Australia. Up until 2015, there was a station located on the outskirts of the state capital - Perth. This was used to communicate to satellites in Low Earth Orbit, as well as other spacecraft during their Launch and Early Orbit Phase (LEOP). This station was recently decommissioned, with the functionality taken over by a new 4.5m dish out at New Norcia - 120km away. Which is the reason for this blog post!!! ( Finally....)

#SocialSpaceWA

Only a few weeks ago, I saw that ESA had put word out via their @social4space Twitter account, that they were going to host an event on 10th and 11th Feb for the inauguration of the new 4.5M dish. It would be a behind the scenes look at one of the few space related facilities here in Australia, and it's in my backyard (not literally!) The event was by invitation only, and people with social media "credentials" could apply to be selected for the event. Now if any of you are as much of a space nerd as I am, then this is one opportunity that wasn't going to be missed! I completed the application process and waited for the announcement of the successful attendees......

YESSSS!!!!! I was invited!!!!!

Myself and about 14 other space geeks are going!! We're going to have an awesome time!

The event will be a mix of socialising, presentations by astronomers, and a behind the scenes look at the facility. 

For updates on the event, follow the various social media accounts of the participants here,  ESAs @Social4Space account on Twitter and the ESA Facebook page. For official event images, there's a Flickr album. 

I'll post updates via a mix of this blog, the @OzQube1 Twitter Account, the OzQube-1 Facebook page and my personal @ssshocker Twitter account. 

More soon!!!!

OzQube-1 CDH Design Complete

I had joked on social media that the CDH had passed the KDR - The Kitchen Design Review. For those not in the know, this is a play on the name of the Critical Design Review (CDR) phase often used in aerospace. In my case, I was being very literal - I reviewed the design in the kitchen! I have settled on a final design for the first revision of the OzQube1 CDH ( Command and Data Handling) board. This is the brains of the satellite. It co-ordinates the recording of data from the various sensors including the camera and the transmission and reception of data from the radio. So what's inside?

The OzQube-1 CDH

The brains of OzQube-1 starts with an Atmel ATmega328P Microcontroller. This is the same microcontroller used in many Arduino boards, and is closest in design to the Arduino Pro Mini 3.3V . It is an 8-bit microcontroller that runs at a leisurely 8 MHz. It has a "massive" 2 Kilobytes of SRAM, and 32 Kilobytes of flash memory. So it's a long way from something like your mobile phone or your computer.

In order to store the image data coming from the camera, a Micro-SD card is also incorporated onto the board. The Micro-SD can also be used to store telemetry data if required.

The next piece is the 9-axis motion tracking IC from Invensense - The MPU-9250. It contains a 3-axis Gyroscope, a 3-axis Accelerometer and 3-axis Compass. This is used to determine the satellites orientation, and the measure the strength of the earth's magnetic field. 

The next critical piece is the RTC (Real Time Clock). This, as the name suggests, is a clock. It can measure time more accurately that the microcontroller can, and uses a lot less power doing it. Unfortunately, because a satellite needs to have all power removed until it is deployed from the launch vehicle, it isn't possible to set the time in advance. It will only start counting once it has been deployed. It is possible to set the time remotely, but as there's no GPS onboard OzQube-1, the time will only be an approximation.

The RTC provides another very useful function, which is a countdown timer. The RTC can alert the microcontroller once a specific period has passed. It is important to do this external to the microcontroller, as microcontroller can sometimes get a bit "distracted" performing other tasks, leading to incorrect time measurements.

The remainder of the CDH is the local power supply arrangement. This includes a Watchdog Timer, which will reset the microcontroller if it hasn't toggled one of its inputs within a specified time. The electronics of the CDH are all 3.3V, but the EPS and Battery have a few different outputs. The EPS provides a regulated 3.3V for the CDH. This is the primary power source. If, for some reason, the 3.3V circuit fails, the CDH has its own circuit to take the battery voltage and regulate it down to the 3.3V required. This isn't as efficient as the EPS, but allows a bit of fault tolerance. Controlling all this is a small control circuit that will automatically switch and prioritise the power source.

Expansion

The main limit I found was the number of pins available on the microcontroller. The TQFP package of the ATmega328P has 32 pins. While I've managed to squeeze all the functionality into this design, I haven't stuck to the full PQ60 design specification. I'm not able to connect all the GPIO pins on the backplane to the microcontroller. 

One possibility is to replace the ATmega328P with another in the Atmel family - the ATmega1284P. This is the same architecture, but has 44 pins, 4 times the flash memory capacity and 8 times the SRAM capacity. It can also be configured to use the Arduino development environment, so it can be programmed the same way. 

Future satellites could use a different microcontroller architecture, but for OzQube-1 I wanted to stick to something that people are familiar with.

Basic PocketQube Power Supply

After posting a couple of pictures on Twitter of the small power supply I'd built for PocketQubes, I thought I'd give a bit more detail in a blog post.

Even though I'm building a different EPS (electrical power system) for my PocketQube "OzQube-1", I wanted a small power supply that could power the satellite while I am testing it.
I had a few requirements:

1. It needs to be able to be powered from a plug pack (wall wart) or from an external battery pack. 
2. It has to fit into the PocketQube PQ60 form factor
3. It needs to output 3.3V and 5V
4. It needs to have a similar current capacity to the real spacecraft EPS
5. Cheap

There is actually a very common thing that already fulfils most of these requirements - the humble breadboard power supply! The main issue is that they don't fit inside a PocketQube.

Fortunately, I have a prototyping solution that's already in the PQ60 PocketQube form factor - ProtoQube.

All that's needed now is a few components.

If you look at a breadboard power supply, they often have a DC jack, and a USB input. The problem with USB is that there's often a 500mA current limit. This wasn't going to work for me, so I opted for a 2 pin screw terminal input. 

Another issue with a breadboard power supply is the the voltage regulators. These are often SOT-223 surface mount parts. This is ok for a custom made power supply, but ProtoQube has a grid of holes, so a through hole regulator is needed. In order to keep the component count down, I went with fixed value voltage regulators. There are many on the market, so I went with some that were readily available - the ST Micro LD1117V50 and LD1117V33. These just need a single bypass capacitor on the input and output, and are capable of 800mA current.

Finishing off the power supply are some pin headers for each rail, and a LED indicator to show when power is connected. I also added a diode on the input for reverse polarity protection. Here's the schematic to show how it's all connected:

Assembling the power supply just requires some additional solid core wire, and the components arranged like you see in the pictures.

All that's needed now is to solder on the Hirose FX8C backplane connector, and some female pin header sockets so I can connect the power supply output to the rest of the stack!