Tip Mass Presentation Anders Fornberg – Team Lead/Imaging


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Tip Mass Presentation

  • Anders Fornberg – Team Lead/Imaging

  • Kate Worster– Power

  • Siddharth Shetty – Comm

  • Jen Getz & Terry Song – Structures

  • Joshua Stamps – Thermal


Overall Mission of the tip-mass

  • Main Mission

    • Provide gravity-gradient stabilization for DINO
  • Functions

    • Capture and send pictures
      • Deployment of FITS
      • Deployment of Aero-fins
      • DINO main module


Top-Level Requirements

  • 5kg mass

  • Tip-Mass shall not connect to DINO other than via the boom

    • Separate power system
    • Wireless communications from DINO to Tip-Mass module
  • Tip-Mass shall meet all NASA safety requirements



General Layout of Tip Mass



Overall Tip Mass Subsystem Test Plan

  • Proper operations of the tip mass when given specific commands

    • Triggering of camera
    • Resetting of camera’s memory
    • Receiving image for camera’s memory
    • Initialization of power save mode
    • Return to non-power save mode
    • Accomplished with software that simulates commands that the flight computer would send to the tip mass
  • “Initial on” counter can initially activate the tip mass subsystem





COMM System Requirements

  • Fast and reliable wireless link

  • Transmit over 6 meter distance (tested over >33m distance successfully without packet loss)

  • Utilizes 5 V DC power line

  • RS-232 Compatible



TPS Options

  • Infrared

  • Bluetooth

    • Recommended Receiver sensitivity: -70dBm
    • Standard not as open as compared the IEEE 802.11
    • Operates in license-free band
  • IEEE 802.11b

    • Open and widely used standard
    • Recommended Receiver sensitivity: -90dBm (higher range)
    • Operates in license-free band


Communication system



Features - WISER 2400

  • Operates In the ISM band (2.4GHz – 2.495GHz), no FCC license required

  • No driver on the host device is required for radio operation

  • Independent of the operating system on the host equipment or device as long as a RS232 port is properly supported

  • Industry standard IEEE 802.11b-compliant wireless interface; Interoperable Client radios from other vendors



Specifications-WISER 2400

  • Frequency: ISM band (2.4GHz – 2.495GHz)

  • Link Distance: ~6 meters in open space

  • Voltage, current: 5v, max 480mA (in transmit mode)

  • Data rate: Capable of supporting up to 115K baud (possible limitation on the digital camera side to transmit data)

  • Weight : 3.7ounces:the radio with case,1.7 ounces is the weight of the case

  • Antenna type: Integrated dipole antenna (omni-directional) with ~2dBi gain



Implementation details

  • One Wiser unit will act as the Access Point and the other will play the role of a station

  • ‘Beacon’ packets show supported data rates of 1,2,5.5,11 Mbps

  • Cap on the serial interface; a 9600 baud rate is currently set (default value), which can be increased up to 115K



Agilent Tool



Radio test results



Link Budget

  • Free space loss in space

  • Lp(dB)= 92,45 + 20log10 F+20 log10d 

  • For 10m L~ 60dB at 2.45GHz and ~70dB for 30m

  • Power at Rx (20m)= 14dBm + 2dBm – 70dB + 2dB = -52dBm ( > Receiver sensitivity of -80dBm)



Power Drain

  • Beacons transmitted at 100msec intervals by Access Point (Infrastructure mode)

  • Effective time of transmission of beacon frames ~ 3.8sec per hour

  • Power drain in Receive mode higher ~250mA

  • Support for power-save mode available

  • Circuitry to cut off power at times of ‘No use’



Future tests

  • Exhaustive radio test to be carried out by attaching the wiser units behind isogrids to simulate actual working conditions and also takes into account the orientation of units

  • Throughput calculations to be performed using programs to transfer bulk data over these units and observing the transmit success rate





Requirements on other TM systems

  • Equipment

  • 4 A-hr NiCad Cells @ 1.2V ea.

    • Charge time 14-16hrs or 1hr
  • MAX1672 DC/DC Power Converter

  • Structure to contain and support battery

  • Fuse, derated; appropriate-sized wires, also derated

  • FET’s or relays for inhibit switching



Power Safety and Operations

  • Safety

  • Two-fault tolerant battery inhibit system

  • No shunt diodes

  • Battery case must contain any leaks and prevent shorts in the battery

  • Fuse must be provided on ground leg of battery

  • System will be un-powered until TM separation from DINO

    • Launch with fully charged battery
    • Need shunt diodes on ea. cell
    • All cell vents must be oriented upward during launch


Power System Requirements

  • Tip Mass Electrical Power System (TM-EPS) must provide 5V regulated line to TM subsystems

    • 802.11b wireless transceiver
    • Digital Camera
  • TM-EPS must provide power for at least 180 minutes

    • Will need to image on at least 3 different orbits
      • Boom deployment
      • FITS deployment
      • Aero-fin deployment
  • TM-EPS will meet all NASA safety requirements

  • TM-EPS will share as many components as possible with DINO main S/C

  • Inhibits and monitors must be able to be verified from Ground Support Equipment (GSE)



TM-EPS Block Diagram



Power System Overview



Power System Action Items



Power Tip Mass Test Plan

  • Proper power levels to each subsystem

    • Communication’s wiser 2400 unit is given a controlled 5 Volt line
    • Imaging’s Jam-Cam is given a controlled 5 Volt line
    • Accomplished using a multi-meter and slightly varying the input voltage to simulate noise
  • Inhibits are operating properly

  • Receives and can initialize power save mode

    • Software that simulates a “power save” command given to power by the FPGA
  • Receives and can initialize non-power save mode

    • Software that simulates a “non-power save” command given to power by the FPGA




Science TP Sub-System Requirements

  • Take clear pictures of FITS and Aero-Fins Deployment and main DINO module

  • Serial connection to FPGA Chip

  • Powered by 5 Volt line

  • Pass all NASA specification on materials

    • No ABS material


Trade Study (Jam-Cams in Tip-Mass)



Canon Powershot S-10 for Tip-Mass



Trade Study Review

  • Due to the boom redesign the tip-mass structure will be positioned closer to the main module. This will require a less resolution camera. Also, because of the faster deployment of such a design, storage time is not such an issue.

  • The ability of the S-10 to use serial and USB could allow for use in main satellite as well as tip mass module.

  • S-10 is a better camera all around except that there are a lot of unknowns



Tip-Mass Camera Decision

  • Jam-Cams will be the primary camera at this point

  • Will do a dual development with the jam-cams and the Canon S-10

  • In the process of purchasing one S-10 to do ABS plastic detection



Preliminary Command list for Science

  • All of Jam-Cams operations can be controlled through the serial Port

  • Camera Power (on/off)

  • Camera Trigger (take picture)

  • Receive images

  • Clear Memory

  • Ping Camera



FPGA Board



Test Plan and future studies

  • Reliable serial connection to FPGA board

  • Program to test commands given to Jam-Cam

  • Test image quality at 6 meters with bright background

  • ABS plastic testing on S-10 with help from main science team





Structures Design Requirements

  • Total Mass: 5 kg

  • Components Mass (estimates):

    • Batteries (including structure): 500-600g
    • Camera (w/o case): 68 g
    • Comm (w/o case): TBD
    • Top Half of the Lightband Deployment System: 2.1 kg
    • Internal Deployment System:
      • Mechanism to deploy: 1.0 kg
      • Attachment Tether: ~1.0 mg
    • Internal/External Support Boxes:
      • Constructed of 6061 Aluminum
      • Density: 2698.79064 kg/m3
    • Ballast will be used as necessary to meet mass requirements.


Structures Design Requirements

  • Total Volume: 420.5 in3

    • Bottom Plate will have a half inch lip to decrease tension and increase stability.
  • Interior Dimensions (estimates):

    • Battery Box: TBD
    • Camera Box: TBD
    • Comm Box: TBD
    • Boom Deployment System Box: 3.5” x 4.0” x 4.0”
  • Center of Mass must be along the z-axis

    • The boom is parallel to the z-axis
    • The length of the boom is 6 meters long


Structures Design Detail

  • The main design driver is the mass requirement

    • The 5kg mass limit is critical in designing every component
  • Maximizing interior space without failing to meet the design requirements

    • Hexagon shape has been selected due to its large volume capacity


Structures Design Detail



Subsystem Test Plan for Tip-Mass

  • COMM

    • Transmit and receive from both FPGA and flight computer
  • Structures

    • Keep on improving the design to optimize structural performance meanwhile meeting mass requirement
    • Testing will be done in coordination with the main satellite
  • Science

  • Power

    • All system power test to ensure 2 hour operation


Issues and Concerns

  • STR

    • Protection for internal components, necessary?
    • Exceeding the mass requirement is still possibly an issue
  • COMM

    • Power drain due to continuous “beacon” transmission
  • PWR

    • Effects on power from tether to boom (if any)
    • MOPS counter vs. switch for initial power on
  • SCI




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