Let there be light

Mathias Nowak

And there was light.

It took us about a week of a very tedious and boring work, but we finally managed to get it done: all of the optical elements (that is: the two mirrors) of the payload are now aligned (well, sort of…). The springs used to  adjust the secondary mirror have been removed, and replaced with peelable washers (I’ll dedicate a specific post to those ones, they deserve it…). Everything is now hold in place by three brand new FHC M3x8 screws, coming straight from the observatory warehouse. By the way, I wonder how many PhD student at LESIA know this place…

With all the optics properly aligned, it it time to get the first serious image of the Point Spread Function (aka PSF) of the PicSat instrument. According to the theory, the PSF should be very close to a 2d gaussian of about 5 or 6 microns (Full Width at Half Maximum).

Starting scan:

[====================] 0%  (the piezo actuators are now purring)

[====================] 50%

[====================] 100%

Done.

Annnnd… here it is! Oh, wait a minute, is it really an 8×12 micron spot that I see here? And is that a secondary lobe over there?

I knew we should have gone for a Cassegrain!

The image of a point source (a single star), as seen by the fiber in the focal plane of the PicSat telescope.

Vibration achieved

ldavid

We just finished the vibration test !

After an EMC problem detected  once the first axis (Z) ran Friday (which perturbed the communication with the PC), we came back this morning to
perform X and Y.
Test went very well and the EMC problem was identified : the inductor of the shaker ! We just put the electric gain of the vibration device off and electronic test was good: temperature regulation, photodiode and piezo-stage check were OK !


Once back in LESIA, we disassembled the payload and put it on our bench to check the optical alignment with a simulated stellar source:

The first obtained PSF is nice, we’ll check with detail but it seems like there is no modification before and after the test.

 

 

 

 

 

 

 

 

 

A bootloader for our payload!

Mathias Nowak

The photo only poorly renders the magnificence of what is happening here: the left diode of this STM32 based development board is actually BLINKING!

… What? A LED blinking software? Is that REALLY what we have been working on during these past few days? Don’t we have better than that to do?

Well, what you don’t know is that in the present case, this simple piece of software was not on the FLASH memory at first, and the LED was not blinking when the STM32 booted. Where did this new code come from, then? From these two orange and yellow wires, connecting the STM32 UART interface to a laptop. Yes, the program was transferred through this exact same interface that will connect the payload to the main computer of the satellite!

What this all means is that we will be able to update and/or reprogram the payload while in-flight! This will be used to correct the bugs to add some exciting new functionalities that we have yet to imagine!

Uh-oh. Did I just lose the perfect excuse to actually go up there with my JTAG connector?

A blinking LED on our STM32 dev board.