|Estimated Requirement||Requirement + contingency|
|Active Power (camera)||40mW||x|
|Active Power (both detectors)||856mW max||1070mW max|
|Active Power (one detector)||518mW max||648mW max|
|Board size (exc. camera, ADCS)||4800mm2 + 20mm clearance||6000mm2 + 20mm clearance|
|External size||2x 1600mm2 + 1x 400mm2||x|
|Cost (development and flight)||$3965||$4165|
Typical power consumption of the detector circuitry is 80mW less than all maximum ratings (96mW w/ contingency)
Tests with the PPB indicate that actual power consumption will be more along the lines of 350mW per detector.
Contact (append @le.ac.uk to all email addresses)
If you have any questions about any part of the payload subsystem, feel free to email Phil or Laura. Bear with us, we're students and sometimes the degree leaves us little time to respond. We will get back to you as soon as we are able.
Payload team leader (for general science enquiries): Philip Peterson (pjdp1)
Payload lab specialist, management, outreach: Laura Evans (lle1)
The satellite will carry two 33mm round MCP dust detectors plated with 40nm Aluminum foil. These will be mounted at right angles to each other outside the satellite's frame, and named 'X' and 'Y' corresponding to the satellite axis they are facing (the Z axis is the one that the camera looks down).
This system definitions document will tell you everything you need to know about the design of the payload and its requirements.
This software interface document describes how to program the detectors on the payload.
This electronics interface document shows which pins to connect to the satellite bus.
This mechanical interface document contains the physical dimensions and details of the payload.
This PPB test plan contains instructions for testing the Payload Prototype Board (PPB).
This report contains calibration data for the payload prototype board (PPB).
This document contains a detailed mass, power, size and cost budget breakdown.
The second laser experiment involved firing a laser at the microchannel plate detector to vapourize the film on the front in much the same way as a micrometeorite impact would. This is an important experiment to help prove the PPB's capabilities, as it supplied power to the detector and handled the resulting signals using it's amplifiers.
Laser test analysis
The HV supply calibration is an important part of characterizing the payload's voltage monitors. The unregulated high voltage supply we are using produces a lower output voltage when under heavier current load, and this varying ratio of output to input voltage can be detected by the monitor circuits and used to give an estimate of the detector's operating current, which in turn is very important for safe plate operation.
- Test plan goes here
- Results document goes here.
The dust bombardment measurements (hopefully at Heidelberg) will test the PPB under conditions that are as close to those in flight as possible. It will involve a final calibration of the payload's gain characteristics, after which the payload board's design can be finalized.
This 4th year project features estimations of the expected dust signal size and of noise sources in LEO
- Vacuum system interface document goes here
- Test plan goes here
- Results document goes here.
Preliminary board layout
System block diagram
This system block diagram is outdated and should show a second redundant DC-DC converter.
Any and all documents that we produce to inform other teams of how the payload works and what it does should be uploaded and put in this section.
Payload and camera work package descriptions
Electronics chain gain calculations
Lab equipment configuration
Lab Multichannel analyzer calibration
Lab general calibration guide
Test plan for the MCP setup
How our MCP detector works
The MCP guide document is probably the best place to start, followed by the gain calculations.
MCA calibration curve graph and data here
The most recent version of the Payload Definition Document is here
Here is some information about dust in the magnetosphere
This report gives extensive information on the NIM electronics, their gain, the operation of the MCP and also has some preliminary analysis of the first laser test carried out in 2009.
Powering the payload - The payload will need access to the 5V bus supply. All the main payload systems use the 5V supply, however the camera requires 3.3V.
The 1kV HV power supply on the payload is isolated from the main bus supply, and the rest of the satellite bus will be protected in case of plate shorts, catastrophic failure of the resistive divider or a fault in the HV power supply.
All pins use 3.3V TTL except the analog output pins, which carry a voltage that can be anywhere between -2.5V and +2.5V. Logic pin ‘High’ refers to 3.3V, and ‘Low’ to 0V. Most of the circuitry in the detector side of the payload is analog and does not require a constant clock frequency or carrier to operate. For reading the Analog out pins, set the computer’s ADC to 5V operating range. Mode 00 (single reading) should be adequate.
- X Signal reset,
- Y Signal reset: Send a short high signal (at least 100ns) to this pin to reset the respective payload signal buffers to zero volts after you have read the signal voltage from it. Hold it low the rest of the time, or the buffer will not work.
- X Support on,
- Y Support on: Hold either of these pins high to power up the electronics chain for the X or Y detector. Obviously, the chain must be powered up for any of the other pins to do any good. Never power up the HV output of a detector without powering on the respective signal chain, as the signal chain also supplies power to the HV supply's voltage monitors.
- X HV on,
- Y HV on: The HV on the plates must be powered up separately to the electronics chain. Drop these pins low to interrupt power to the HV supply.
- HV set x1,
- HV set x2,
- HV set x4: These three pins control a 3-bit digital-analog converter circuit that varies the voltage across both the detector plates between 1000V and 1150V. Set a pin high to set its respective bit.
|HV set x4||HV set x2||HV set x1||Expected HV input reading||Expected HV output reading||Approximate plate voltage|
The first six pins listed here are analog output pins and carry various analog signals from the payload to the OBDH. They should be tied to the OBDH ADC on port 6. The signal pins carry an analog voltage range of zero to five volts referenced from common ground.
- X HV input voltage,
- Y HV input voltage: The voltage on this analog output pin is the same as the voltage going into the HV supply that biases the MCP.
- X HV output voltage,
- Y HV output voltage: The voltage on this analog output pin is equal to one three hundredth of the voltage output of the HV supply, and approximately two fifths of the plate voltage. See figure 1 for voltage information.
- X Detector signal,
- Y Detector signal: The buffered analog output of the signal processing chain waits on this pin for the computer to read and then reset it.
- X Signal received,
- Y Signal received: This pin will go high if there is an event in the specified detector since the last time the signal was reset, and low if not.
Electronic component documentation
Information and datasheets on the major components of the payload's circuitry.
Choosing_a_DAC - digital to analog converter (in house production)
DAC test plan
High Voltage Power Supply (Emco Q12N-5)
Voltage/Current monitor circuit (In house production)
High voltage control/DAC (In house production)
Buffer simulation report (in house production)
Charge sensitive preamplifier (AmpTek A250)
Shaping amplifier (AmpTek A275)
Sample hold version 2 test report
±5V power converter for amplifiers (RECOM RM0505S)
General information about amplifier electronics here
Signal amplification system schematic
Noise in the signal processing chain connected to MCP here
4th year project/feasibility study for the light flash detector is here
SRIM tool for looking at charged particle background here
Filter transmission tool for looking at EM transmission of nanofilm and MCP here
A first draft Science Requirements Document can be found here
An overview of detector design options is available here
A summary of the advice meeting with Tim Stevenson can be found here
In the case of the nanometeoroid dust detector, one of the most important questions is the flux the device would see, and the accessible size regimes.
Detectable flux as a function of foil thickness - comparison between the Micro Abrasion Package (MAP) on the Long Duration Exposure Facillity (LDEF) and an MCP based detector
Comparison of empirically verified flux regimes to sizes theoretically accessible by MCP detector
For information about the Grün interplanetary flux model see Spenvis website
The Grün model was used to create this table showing the expected flux of particles above a certain size onto one side of the CubeSat over 9 months.
I thought I'd add some information about Beta meteoroids that I found. It was in the forum, but I thought it might be better here
External payload finite element analysis
For anyone who wants to see the page for calculation of the equilibrium temperature of opaque aluminium, go here.