DINO Safety Review DINO Communications Team Hosam Ghaith

DINO Safety Review DINO Communications Team: Hosam Ghaith Mike Li Zach Allen Colorado Space Grant 1

Bonding and Grounding n n n Satellite Structure must be bonded to the ICU chassis ground to prevent charge accumulation Resistance between any payload point and the Orbiter must be less than 1 Ohm. Bonding can be achieved by metal-to-metal contact, or by conductive coating and surface treatments. Colorado Space Grant 2

Example n n Calculate the total resistance between points A and B. Worst case scenario: the two 0. 0025 Ohm resistors are not grounded, and total resistance is 0. 810 Ohms (less than 1). Colorado Space Grant 3

Different Bonding Methods n n Alodine or chemical conversion: helps to prevent corrosion and, thus, strengthens bonds. Bare metal to metal contact guarantees conductivity Bonding strap: conductive and also secure bonding Anodizing both parts is NOT a good bonding method: results in insulation, not conductivity. Colorado Space Grant 4

Grounding n Core ICD document 10. 7. 4. 1 and 10. 7. 4. 3 states that “the Orbiter D. C. power return from a Cargo element shall be … D. C. isolated from structure ground in the Cargo element by a minimum of 1 Mega Ohm. ” Colorado Space Grant 5

Example n The following scheme does not satisfy the requirement: need an extra 1 MΩ resistor between ground and negative side of battery Colorado Space Grant 6

SIP n n n The resistance between any point on the Nanosat and the satellite interface panel (SIP) must always be less than 2. 5 milli Ohms. Why? To prevent excessive heating or thermal dissipation To prevent static build-up (which may damage some parts). Colorado Space Grant 7

Fault-Tolerance (Fixed Antenna) n Electrical inhibits (interruption feature) are not necessary q q No mechanical/pyrotechnic functions Fuses? Colorado Space Grant 8

Fault-Tolerance (Deployable Antenna) n Accidental deployment prevention q q q Premature deployment could affect Orbiter operation (Catastrophic Hazard)1 Minimum of 3 independent inhibits (2 fault tolerant)2 Need one independently controlled inhibit in the ground return path 3 1. 2. 3. 202. 4 – “SPECIFIC CATASTROPHIC HAZARDOUS FUNCTIONS: Planned Deployment/Extension Functions ” 201. 3 – “must be controlled by a minimum of three independent inhibits” 201. 3 – “the ground return for the function circuit must be interrupted by one of the independent inhibits” 4. Section numbers refer to NSTS 1700. 7 B Colorado Space Grant 9

Power Concerns n COMM system meets Unpowered Bus Exception 1 q q COMM might have catastrophic hazards System is de-energized prior to payload deployment Relay 1 Relay 2 Battery Satellite Subsystem Critical Hazard Satellite System Catastrophic Hazard Relay 3 1. 2. 201. 1 c(3): Unpowered Bus Exception Section numbers refer to NSTS 1700. 7 B Colorado Space Grant 10

Question 14: Nanosat Power System Inhibit 1 Inhibit 2 Inhibit 3 Deployable Antenna Solar array RF System Inhibit 4 Colorado Space Grant 11

Safety Exam, Question 14 n Two extra independent inhibits needed: q q n n 1 inhibit between the solar panel positive output and battery. 1 inhibit in solar array ground return path, between solar array and battery. Inhibits do not need to be monitored for RF system because it is not more that 6 d. B over ICD limits. Inhibits need to be monitored since only 3 between battery and antenna mechanism Colorado Space Grant 12

Transmissions n Two types of transmissions q Cargo Bay Doors Closed n q Max. intentional radiated field of 0. 5 V/m 1 Cargo Bay Doors Open n Payload to orbiter limit of 4 V/m 2 1. ICD 2 -19001 section 10. 7. 3. 2. 2. 2. 1 2. ICD 2 -19001 diagram 10. 7. 3. 2. 2. 2. 1. 2 -1 Colorado Space Grant 13

Diagram 10. 7. 3. 2. 2. 2. 1. 2 -1: Payload to Orbiter Field Limit Colorado Space Grant 14

RF Power Levels n NSTS 1700. 2 B section 202. 5 d: q n “For payload transmitters in the payload bay or crew cabin, three independent inhibits are required whenever the intentional radiation would exceed the ICD limits and is assessed as hazardous. ” NSTS 1700. 2 B section 202. 5 e: q “RF transmitter inhibits do not require monitoring unless the radiation levels would exceed the ICD allowable levels by more than 6 d. B in which case two of three inhibits must be monitored. “ Colorado Space Grant 15

Potential Interference with STS Communications n 919 Communication Channels q Channel 1 through 801 (STDN) n q Channel 850 through 882 (NASA DSN Deep Space Network) n Colorado Space Grant Receive Frequencies 2200 MHz to 2300 MHz Receive Frequencies 2290. 185185 MHz to 2299. 814815 MHz 16

Potential Interference with STS Communications n Channel 900 through 919 (DOD/SGLS) q n Closest Potential frequency: Tip Mass Wireless Ethernet Transmitter q n 2202. 500 MHz to 2297. 500 MHz 2412 MHz to 2462 MHz DSSS (Direct Sequence Spread Spectrum) Close to 6 th harmonic of 400 MHz Ham Band Colorado Space Grant 17

Conclusion n Communication Subsystem will probably have at least one catastrophic hazard q q n Deployable Antenna Transmit Power? Will not know if hazard is critical or catastrophic until Communication System is designed further Colorado Space Grant 18