UNITEC-1 signal reception system

Details of the electric wave reception of UNITEC-1 are shown in the following.
Please refer the reception of the electric wave.

• UNITEC-1 specification
• Receiver system
• Antenna control system
• Characteristic of down converter (MKU 57 G3 432-429) made by Kuhne company
• Change of transmit frequency with UNITEC-1 equipped with transmitter
• Down-link data
• Signal analysis and decipherment
• Orbit information

UNITEC-1 specification

Communication specification

Left,Figure 1. Patch antenna for down-link equipped in UNITEC-1
Right,Figure 2. antenna arrangement chart. One patch antenna is arranged on each opposite side respectively.

Launch date: 06:58:22, May 21, 2010 (JST)
Launch Vehicle: H-IIA Launch Vehicle No.17(for PLANET-C)
Location: Tanegashima Space Center
Launch form: Riding together PLANET-C.

UNITEC-1 separation

(definition of position and speed (inertial frame of reference))
the origin of the coordinate axes:Earth
X axis:Direction of intersection of meridian and equator including Greenwich of nominal lift off time.
Y axis:Right-handed system (in the equatorial plane)
Z axis: Direction of the North Pole

Receiver system

<< Upper >>
[ 5840.000MHz RF signal from UNITEC-1 ]

• > Dish antenna
• > LNA
• > Down converter (5840GHz > 435MHz) made by Kuhne company
• > Filter (diplexer)
• > [ utput 435MHz IF signal ]

<< Lower >>
[ Output 435MHz IF signal ]

• > Receiver (AR-ALPHA, made by AOR company)
  
  * It only has to be a receiver that can receive the IF signal of 435MHz.
  * Icom910 and Perceurs, etc. can be used as a receiver. However, remodeling the receiver is needed.
• > [ AF line output ] or [ I/Q output ]
• > PC (takes and analyze)

Antenna control system

The size of the antenna was roughly classified into the small caliber of 10m or less in diameter and the large caliber of 10m or more. Three antennas of the small caliber and three antennas of the large caliber were maintained in this project. The regulating system and accuracy, etc. are different in each earth station because an original usage is different according to the antenna. Details are not described here.

Characteristic of down converter (MKU 57 G3 432-429) made by Kuhne company

In this project, the down converter that converted the signal of C-band 5840MHz into 435MHz was prepared. Figure 3. is an output signal from down converter + filter (diplexer) made by the Kuhne company when you input 5840MHz signal of -60dBm that generates it with Signal Generator(SG).

Figure 3. IF signal input to AR-ALPHA

Change of transmit frequency by UNITEC-1 equipped with the transmitter

The reference frequency is 5840.000MHz.
However, the change of the transmit frequency by the temperature is confirmed as a characteristic of the communication apparatus installed in UNITEC-1. The change of about 3.5kHz was observed when it was large in 40 minutes. As for the receiver, the one that this change can be allowed is demanded.

Figure 4. Transmission frequency change of UNITEC-1 communication apparatus

Down-link data

The majority of the down-link data is CW signal of 1bps. "CW signal of 1bps" mentioned here is to express 1 and 0 by turning the signal of 5.84GHz on and off every second.

Figure 5. Image of 1bps CW signal

Modulation method AFSK/FM and the data signal of 1200bps are inserted at intervals of above-mentioned 1bpsCW. The distribution in the down-link data of the AFSK/FM signal has been reduced as a design manual. Because the AFSK/FM signal is smaller than CW about reception electric power ratio in the ground.
The communication repeats a series of data transmission defined, "major cycle". One major cycle takes six hours. The composition at the major cycle is as shown in Table 3. It is time zone that data is actually transmitted from the satellite written [ transmission ] in the table. The main computer equipped with UNITEC-1 sends the instruction to the computer that each university developed, and the confirmation examination is done when the time zone of "UOBC survival competition". The result is transmitted to the ground when major communication of transmission.

(orbit presumption communication)
"1" is transmitted 120 times. In a word, the electric wave of the constant output keeps being transmitted for 120 seconds. Necessary data(Arrival angle profile electric wave / Doppler frequency) for the orbital estimation is used for the operation to acquire it in the ground station.

(major communication)
It is a communication including the housekeeping data and the science data, etc. The content of the communication is as shown in Table 4. Data from the computer of each university is transmitted by AFSK/FM. Housekeeping data, science data, a computer test result of each university, and detailed data from each university computer are opened to the public on the Web.

(minor communication)
It is a communication including the housekeeping data and the science data, etc. as well as the major communication. However, it doesn't contain data from the computer of each university, and the AFSK/FM transmission is not done. The content of the communication is as follows.

Signal analysis / Decipherment

The output from the receiver is recorded as AF signal (WAV file). And, the text data is obtained by using Spectran V2 after it converts it if necessary.
The decipherment software is being developed now.
We opens it to the public when development is completed.

Orbit information

On an official Web site of UNITEC-1, orbit information needed to pursue UNITEC-1 opens the one that the orbit of the following seven points was calculated to the public.

• Tohoku University Ground Station ( latitude:? longitude:? high degree:? )
• Katsuura City,Chiba, Katsuura Tracking and Communication Station ( latitude:35.2 longitude:140.016667 high degree:180 )
• Kashima city,Ibaraki, Kashima space technological center ( latitude:35.9533 longitude:140.6667 high degree:32 )
• The University of Tokyo, Ground Station ( latitude:35.712 longitude:139.76 high degree:43 )
• Wakayama, Misato astronomical observatory ( latitude:34.2678 longitude:135.1516 high degree:? )
• Yamaguchi Ground Station ( latitude:34.2161 longitude:131.5572 high degree:144 )
• Kyushu University, Ground Station ( latitude:33.5988 longitude:130.2120 high degree:79 )

As for disclosed orbit information, it is scheduled that the following observational result launches and uses, calculates again, and is updated.
The orbit analysis software when an arbitrary location information is input, orbit information is obtained is opened to the public on an official Web site of UNITEC-1.