COMM Subgroup

Tomo Sugano (Primarily served as COMM personnel)

• Tasks– Started out by helping Relative Orbit team

with differential delta-V requirement and GN2 mass

– Communication Scheme of the mission– System Integration (on-board flight

computer)

Tomo Sugano (1/15)

Differential Drag Compensation

• Ballistic coefficients different between satellite and shuttle

• Difference in drag forces (i.e. acceleration) exists.

• (B-Coeff. of Shuttle) >> (B-Coeff. of Satellite)

• Satellite must expend Delta-V to keep up with space shuttle.

Tomo Sugano (2/15)

Computations• Atmospheric drag acceleration (Da):

• Drag acceleration difference between the two spacecraft:

STS: S = 64.1 m2, CD = 2.0, m = 104,000 kg (orbiter typical)

Sat: S = 0.385 m2 (nominal), CD = 3.0 (worst case), m = 50 kg

Tomo Sugano (3/15)

Computations (cont’d)

• Orbiter speed (assuming circular orbit)

• Definition of Delta-V (or specific impulse)

• Mass expenditure of propellant (i.e. GN2 cold gas)

Tomo Sugano (4/15)

Results

• Using Isp = 65 sec; assume 50 kg for satellite weight

• Conclusions- At the typical 300 km LEO, Delta-V for 1 day mission is 1.36 m/s- Satellite will need at least 107 grams of GN2 to compensate drag- In addition to this Delta-V, we have orbit transfer Delta-V and ADCS Delta-V.

How we determined tank size.

Tomo Sugano (5/18)

COMM: Overview

• Receive data from the space shuttle

• Transmit data to the space shuttle

Satellite

Computer

Tx

Rx

Wireless LAN Transceiver

SatelliteSatellite must be able to:

Space Shuttle Orbiter

Receive Commands

Transmit PhotosTomo Sugano (6/15)

COMM: Operational Schematic

Satellite Space Shuttle

FCSCPU

ImageBuffer

ArchivalMemory LAN

Tx

TxRx

RxDownlink

DownlinkUplink

Uplink

LANRAM

Data Flow

Tomo Sugano (7/15)

CPU

COMM: Communication Devices

Local Area Network (LAN) Protocol is utilized.

Satellite- A Zonet light-weight

wireless LAN transceiver

Space Shuttle- An integrated wireless

LAN transceiver of a Panasonic Toughbook

Tomo Sugano (8/15)

COMM: Zonet Wireless LAN USB Adapter

• Model: Zonet ZEW2502 802.11g USB Adapter

• Dimensions: 93.5 x 27.5 x 10 mm • Mass: 32.0 grams• Transfer Rate: 54Mbps (nominal)• Uplink (Receive): 260 mW• Downlink (Transmit): 350 mW• Frequency: - 2.412GHz ~ 2.4835GHz

- S-band (space approved, open band)Tomo Sugano (9/15)

COMM: Antenna Modification

• Zonet LAN adapter uses “Microstrip antenna.”

• Compact and reliable for short-distance communication.

• Directly attach antenna on the face of satellite

Tomo Sugano (10/15)

COMM: Image Transfer

• Estimated size of each image: 14-16 Mb• Our LAN protocol and devices allow nominal

54Mbps with pier-to-pier method.• Virtually no cause of appreciable noise in

space between satellite and space shuttle• Transfer time of each image: less than a few

seconds.• Image buffer need not to be large - A few GB USB jump drive recommended.

Tomo Sugano (11/15)

Selection of System Integration CPU

• System integration is core of the FCS Selection of flight computer CPU

• Arcom VIPER 400 MHz CPU found viable• VIPER is suitable because of its

- Light weight, 96 grams- Operable temperature range

-40 C to + 85 C- Windows Embedded feature

easy to program- Computation speed, 400 MHz- Memory capacity, up to 64MB of SDRAM- 5 serial ports- USB ports enables utilization of Zonet LAN adapter & jump drive

VIPER CPU board top view

Tomo Sugano (12/15)

Control System Integration - Overview

• ADCS and Orbit Rectification Computations

• Execute ADCS and Orbit Rectification• In-flight image capture handling • Data archiving

Tomo Sugano (13/15)

System Integration – Overall Scheme

Flight Computer

FCS COMM

Sensors

POWER

ADCS Output

Orbit Control Output

Other Outputs

Tomo Sugano (14/15)

System Integration – Data Connections

Star Tracker Spin Wheels GPS1Thrusters GPS2

Flight Computer

FCS

POWER

Serial 1

Serial 2 Serial 3 Serial 4 Serial 5

PWR FlowUSB 1 USB 2

Wireless

LAN

Archival Memory

Camera

Digital I/O

Tomo Sugano (15/15)

Conclusion

Thank you for your attention!