JP2002324041A - Star sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a star sensor that stores data in a single memory. SOLUTION: The star sensor, that is installed on a satellite, having a bus, a single memory that is connected to the bus to store the data, a data input/ output part that is connected to the bus to get access to the memory for inputting/outputting of the data, a central processing part that is connected to the bus to control the satellite using the data inputted into the memory, an arbitration part, that conducts arbitration of the occupancy of the bus, permits the occupancy of the bus by the data input/output part only while the data input/output part gets access to the memory, and if the data input/ output part terminates the access to the memory, returns the occupancy of the bus to the central processing part is provided. The data input/output part is at least one of an image input part for inputting the image data of a fixed star, a reception command input part that receives a command, from the ground, to input it, and a telemetry transmission part that reads out telemetry data acquired by telemetering from the memory to output it to the ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a satellite mounted on a satellite,
The present invention relates to a configuration of a star sensor that measures the position of a star or the like to determine the attitude of a satellite.

[0002]

2. Description of the Related Art A star sensor mounted on a satellite performs predetermined processing on image data of a photographed star or the like, measures its position, and detects and controls the attitude of the satellite. More specifically, the star sensor acquires image data of a star or the like using a two-dimensional image sensor (CCD) and stores it in a unique image storage memory without any processing. After the storage, the control device accesses the memory to perform predetermined processing on the image data.
The star sensor is usually provided with a plurality of CCD cameras, each of which is provided with an independent and separate image storage memory.

[0003]

In the conventional star sensor, a plurality of independent image data storage memories are provided, so that a memory used for other purposes must be further provided. For example, to store a program of a central processing unit for performing image processing, to store a command for controlling a satellite received from the ground, and / or
Alternatively, it is a memory for storing telemetry data (telemetry data) to be transmitted to the ground.

[0004] It is an object of the present invention to provide a star sensor that stores data in a single memory.

[0005]

A star sensor according to the present invention is a star sensor mounted on a satellite, comprising: a bus;
A single memory connected to a bus for storing data, and a data input / output unit connected to the bus and accessing the memory for inputting / outputting the data, wherein stellar image data is input as the data An image input unit, a reception command input unit that receives a command from the ground and inputs it as the data, and a telemetry transmission unit that reads out telemetry, which is data obtained by telemetry, from the memory as the data and outputs the data toward the ground. At least one data input / output unit, a central processing unit connected to the bus and controlling the satellite using the data input to the memory, and an arbitration unit for arbitrating occupation of the bus, comprising: The data input / output unit acknowledges the occupation of the bus only while the unit accesses the memory, and when the data input / output unit finishes accessing the memory, the central processing unit A star sensor and an arbitration unit to return the occupation of the bus, thereby the objective described above being achieved.

The star sensor further includes a memory interface unit that receives a clock for inputting and outputting the data from the data input / output unit and outputs a control signal for requesting bus occupation to the arbitration unit. The data output unit may be allowed to occupy the bus based on the control signal output from the memory interface unit.

[0007] The first bus width of the bus connecting the memory and the arbitration unit is larger than the second bus width of the bus connecting the data input / output unit and the arbitration unit. And the data may be stored in a predetermined amount and output to the memory, or the data read from the memory may be output to the data input / output unit according to the second bus width.

When the data is image data, the image processing apparatus further includes a comparing unit that compares a threshold value with the size of the image data and outputs a comparison result, and the arbitration unit performs data input / output based on the comparison result. Alternatively, it may be determined whether or not the occupation of the bus is permitted to the unit.

[0009] The star sensor may further include an operation unit that receives the image data and performs an operation for controlling the satellite instead of the central control unit when the data is image data.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 4 of the present invention will be described below with reference to the accompanying drawings. It is assumed that components denoted by the same reference numerals in the drawings describing each embodiment have the same function.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a star sensor 10 according to a first embodiment. The star sensor 10 is a sensor mounted on a satellite for detecting and controlling the attitude of the satellite. The detection of the attitude of the satellite is performed based on the image data obtained by photographing a star or the like and the position of the camera and the like.

The star sensor 10 includes an image input unit 101
, Reception command input unit 102, telemetry transmission unit 1
03, the memory interface unit 104, and the arbitration unit 1
05, the memory 106, and the central processing unit 107 (hereinafter, referred to as
"MPU 107"). These components are connected via an internal bus. The internal bus only transfers data between two components at a certain time. This is to prevent data conflict.

First, the image input unit 101, the reception command input unit 102, and the telemetry transmission unit 103 will be described. These function as data input / output units that access the memory 106 and input / output data, and are also referred to as “data input / output units 101 to 103” below. The image input unit 101 is a two-dimensional imaging device (CCD) camera for acquiring an image of a star as image data. The image input unit 101 outputs image data at a certain timing based on an image input clock. The reception command input unit 102 is a receiver that receives a command for satellite control or the like received from the ground and inputs the command to the star sensor 10. The reception command input unit 102 outputs a command at a certain timing based on the reception command clock. The telemetry transmission unit 103 is a transmitter that transmits telemetry to the ground. Telemetry refers to data obtained by telemetry. In the following description, it is assumed that the telemetry has been acquired in advance and stored in the memory 106. The telemetry transmitting unit 103 outputs the telemetry stored in the memory 106 to the ground at a fixed timing based on the telemetry clock. The data input / output units 101 to 103 also output each clock to the memory interface unit 104.

Next, the memory interface unit 104
Data input / output units 101 to 103 and an arbitration unit 10 described later
5 and mediates the transfer of data between them. More specifically, when receiving a clock from the data input / output units 101 to 103, the memory interface unit 104 generates and outputs a control signal for requesting occupation of the bus in order to access the memory. Here, the clock is an image input clock, a reception command clock, and a telemetry clock. Therefore, different types of data such as image data and commands are stored in the memory 106.
, The arbitration unit 105 can arbitrate the internal bus based only on the control signal.

The arbitration unit 105 occupies the internal bus when the data input / output units 101 to 103 access the memory 106 via the memory interface unit 104, and controls the MPU
The arbitration 107 occupies the internal bus when accessing the memory 106. As a result of the arbitration, the arbitration unit 105 stores in the memory 1
06 to output a control signal. The memory 106 is a single memory that stores image data, commands, telemetry, and a computer program for operating the MPU 107. The MPU 107 is a central control unit as a computer that controls a satellite using the data input to the memory 106.

In this embodiment, only one memory 106 is provided, and no dedicated memory such as a memory for storing image data is provided. Therefore, the arbitration unit 105 that arbitrates which component occupies the internal bus to access the memory 106 is required. The feature of the invention in the first embodiment is that the arbitration unit 105 is
When the data input / output units 101 to 103 complete the access to the memory 106, the MPU 107 notifies the MPU 107 of the bus. Is to return occupancy. By operating as described above, the image data, the command, the telemetry, and the computer program of the MPU 107 can be stored in the single memory 106 as described above, and the number of parts can be reduced as compared with the case where the separate memories are provided. The cost can be reduced.
Further, there is an effect that reliability is improved because the number of components is small. This is very useful on satellites that cannot be easily repaired.

Hereinafter, the operation of the star sensor 10 will be described. As a normal operation, the MPU 107
Have access to This is because the data stored in the memory 106 needs to be processed in order to control the satellite. The MPU 107 transmits address information and the like necessary for reading or writing data to the memory 106 as a control signal to the memory 106. Also MPU1
07 transmits / receives data read from the memory 106 or data to be written to the memory 106 to / from the memory 106.

Next, when the data input / output units 101 to 103 request access to the memory 106, specifically, when storing image data or commands received from the ground in the memory 106, or reading out telemetry from the memory 106. The operation in this case will be described. Hereinafter, a case where the image input unit 101 accesses the memory 106 and stores the image data will be considered as an example.

As described above, the image input unit 101 inputs image data based on the image input clock to the memory interface unit 104 together with the image input clock. Upon receiving the image input clock, the memory interface unit 104 generates a control signal for requesting the occupation of the bus in order to immediately access the memory, and outputs the control signal to the arbitration unit 105.
The arbitration unit 105 receives a bus arbitration signal (low-level R) for stopping the MPU 107 from accessing the memory 106 based on a control signal from the memory interface unit 104.
EQ signal) to the MPU 107. The bus arbitration signal for stopping the access is a signal requesting that the MPU 107 release the occupation of the internal bus. Upon receiving the bus arbitration signal, the MPU 107 transmits an authentication signal (low-level ACK signal) to the arbitration unit 105 to notify the MPU 107 that access has been stopped and that the occupation of the internal bus has been released. At this time, the arbitration unit 105 has the right to occupy the internal bus. As a result, the image data transmitted from the image input unit 101 (FIG. 1) to the memory interface unit 104 (FIG. 1) is transmitted to the memory 106 together with the control signal as memory data via the arbitration unit 105 (FIG. 1). Stored in the memory 106.

On the other hand, when the transmission of the image data to the memory 106 is completed, the arbitration unit 105 immediately transmits a bus arbitration signal (high-level REQ signal) to the MPU 107,
A process for returning the occupation of the internal bus to the MPU 107 is performed. Upon receiving the bus arbitration signal, the MPU 107 transmits an authentication signal (high-level ACK signal) to the arbitration unit 105 to notify that the MPU 107 has acquired the occupation right of the internal bus.

FIG. 2 is a timing chart of signals transmitted and received by the star sensor 10. As described above, FIG. 2 shows the bus arbitration signal (low-level signal) after receiving the image input clock when inputting the (N−1), N, (N + 1) th sampled image data. The timing until the REQ signal is generated is indicated by an arrow. According to FIG. 2, it is understood that the memory data from the arbitration unit is generated simultaneously with the authentication signal (low-level ACK signal) from the MPU 107 (FIG. 1). The memory data is data transmitted from the arbitration unit 105 (FIG. 1) through the internal bus to the memory 106 (FIG. 1). After the input of the image data is completed, the memory data is transferred to the MP by the bus arbitration signal (high-level REQ signal) and the authentication signal (high-level ACK signal).
It is also understood that the data has been changed from U107 (FIG. 1). Note that “A” in FIG.
(B) indicates data transmitted and received between the memory 106 (FIG. 1) and “B” indicates data transmitted and received between the MPU 107 (FIG. 1) and the memory 106 (FIG. 1). Is shown.

The above description is based on the image input unit 101 (FIG. 1)
Is an operation when the image data is stored by accessing the memory 106 (FIG. 1). This is an access to the memory 106 (FIG. 1) by the received command input unit 102 (FIG. 1) (operation for storing the command). The same applies to the case where the telemetry transmitting unit 103 (FIG. 1) accesses the memory 106 (FIG. 1) (the operation of reading the telemetry). For example, the reception command clock related to the Nth command clock is the reception command input unit 102 (FIG. 1).
From the memory interface unit 104 (FIG. 1). With continued reference to FIG.
05 (FIG. 1) immediately outputs a low-level REQ signal and requests the MPU 107 (FIG. 1) to release the bus occupation right. In response to this, the MPU 107 (FIG. 1) outputs a low-level ACK signal to notify the arbitration unit 105 (FIG. 1) that the bus occupation right has been released. And the arbitration unit 105
(FIG. 1) receives a command from the received command input unit 102 (FIG. 1) via the memory interface unit 104 (FIG. 1), and transmits it as memory data to the memory 106 (FIG. 1) together with a control signal. The memory 106 (FIG. 1) stores the command. Upon completion of storing the received command, the arbitration unit 105 immediately outputs a high-level REQ signal and transfers the bus occupation right to the MPU 107 (FIG. 1).
The MPU 107 (FIG. 1) outputs a high-level ACK signal to acquire the right to occupy the bus, and restarts access to the memory 106 (FIG. 1).

It should be noted here that the image input unit 101
(FIG. 1), the reception command input unit 102 (FIG. 1), and the telemetry transmission unit 103 (FIG. 1) operate at timings based on the respective clocks. Bus occupancy must be arbitrated. As a result, the “REQ” signal of FIG.
As understood from the “ACK” signal and the “memory data”, the arbitration unit 105 (FIG. 1) occupies the bus only while the data input / output units 101 to 103 access the memory 106 (FIG. 1). Is released from the MPU 107 (FIG. 1), and immediately after the data input / output units 101 to 103 finish accessing the memory 106 (FIG. 1), the occupation of the bus is returned to the MPU 107 (FIG. 1).

As described above, according to the second embodiment, the arbitration unit acquires the bus right only for the time necessary to store the image data and the reception command in the memory and to read the telemetry from the memory. At other times, the MPU acquires the bus right. As a result, even if a single memory is shared as a storage area for computer programs, image data, commands, and telemetry, the data processing capability of the MPU can be maintained as compared with the case where memories are separately provided.

(Embodiment 2) In Embodiment 2, the bus width of the bus connecting the memory and the arbitration unit is larger than the bus width of the bus connecting the data input / output units 101 to 103 and the arbitration unit. Then, a data storage unit for storing a predetermined amount of data is provided in the arbitration unit. Thereby, more data can be stored in the memory by one access.

FIG. 3 shows a star sensor 30 according to the second embodiment.
FIG. 3 is a block diagram showing the configuration of FIG. The components denoted by the same reference numerals as those of the star sensor 10 (FIG. 1) are the same components as those of the star sensor 10 (FIG. 1), and thus description thereof will be omitted.

First, the bus width not mentioned in the star sensor 10 (FIG. 1) will be described. In the second embodiment, the memory 1
06 (ie, the bus width of the memory 106) connecting the arbitration unit 301 to the data input / output units 101 to
The width of the bus connecting the connection 103 and the arbitration unit 301 is larger than the bus width. In FIG. 3, as an example, the image input unit 101
Alternatively, the bus width of the bus connecting the reception command input unit 102 and the memory interface unit 104 is L, and the bus width of the bus connecting the memory 106 and the arbitration unit 301 is 2L. The bus width between the telemetry transmitting unit 103 and the memory interface unit 104 may be L.

Next, the arbitration unit 301 will be described. FIG.
FIG. 4 is a block diagram illustrating a data storage unit 401 of the arbitration unit 301. The data storage unit 401 of the arbitration unit 301 stores data of two samples of the image input unit 101 (FIG. 3) or the received command input unit 102 (FIG. 3) and stores the data in the memory 106.
(FIG. 3). On the other hand, memory 1
06 (FIG. 3), a function of reading telemetry for two samples with a data width of 2L, dividing the read telemetry into a data width L corresponding to a bus width L between the telemetry transmission unit 103 and the memory interface unit 104, and outputting the data. Also have. The former case will be described as an example. Data storage unit 40
Assuming that data (N-1) has already been stored in 1
When the next data (N) is input, the data storage unit 401 further stores the data (N). And
For example, when the next data (N + 1) is output, data (N-1) and data (N) are output simultaneously. The output destination is the memory 106 (FIG. 3). At this time, the data (N
-1) and data (N) are data output from the image input unit 101 (FIG. 3) and the received command input unit 102 (FIG. 3), and have the same data bit width L.

Hereinafter, this operation will be described with reference to a timing chart. FIG. 5 is a timing chart showing the operation of the arbitration unit 301 (FIG. 4). For example, when the (N + 1) -th sampled image data is input from the image input unit 101 (FIG. 3) to the star sensor 30, the arbitration unit 30
1 (FIG. 3) immediately outputs a low-level REQ signal,
It requests the MPU 107 (FIG. 3) to release the bus occupation right. In response to this, the MPU 107 (FIG. 1) outputs a low-level ACK signal to notify the arbitration unit 301 (FIG. 3) that the bus occupation right has been released. In response, the mediation unit 30
1 (FIG. 3) simultaneously outputs the data (N-1) and the data (N) that have been stored in the data storage unit 401 (FIG. 4). This is apparent from the fact that the control signal at the time of inputting the data (N + 1) is “A” indicating data transmitted and received between the arbitration unit 301 (FIG. 3) and the memory 106 (FIG. 1).

As described above, according to the second embodiment, the MPU 107 (FIG. 3) is provided with a data storage unit for storing data in the arbitration unit and transmitting / receiving data to / from a memory whose bus width is wider than the other bus widths. ) Can access the memory more frequently, and the data processing ability is improved.

(Embodiment 3) In Embodiment 3, the size of image data is compared with a predetermined threshold value, and arbitration is performed based on the comparison result to determine whether to store the image data in the memory.

FIG. 6 shows a star sensor 60 according to the third embodiment.
FIG. 3 is a block diagram showing the configuration of FIG. The components denoted by the same reference numerals as those of the star sensor 10 (FIG. 1) are the same components as those of the star sensor 10 (FIG. 1), and thus description thereof will be omitted. Hereinafter, the comparator 601 and the arbitration unit 602 of the star sensor 60 will be described. The comparator 601 is a comparator that receives image data input by the image input unit 101, compares the image data with a preset threshold value, and outputs a magnitude. The comparison result is output to the memory interface unit 104 and then sent to the arbitration unit 602.
If the image data is larger than the threshold value, the arbitration unit 602 arbitrates the occupation right of the internal bus so that the image data is stored in the memory 106.

As described above, according to the third embodiment, the comparator 601 and the arbitration unit 602 are provided, and only the image data larger than the threshold value is stored in the memory. Compared to the case where all data is stored in the memory, the frequency of the operation of storing the data in the memory is reduced, and the efficiency of data processing can be improved. this is,
This is useful when the on-board star sensor only needs data larger than the threshold.

(Fourth Embodiment) In the fourth embodiment, the operation to be performed by the MPU based on the data stored in the memory is performed by a separately provided processing unit before storing the data in the memory.

FIG. 7 shows a star sensor 70 according to the fourth embodiment.
FIG. 3 is a block diagram showing the configuration of FIG. The components denoted by the same reference numerals as those of the star sensor 10 (FIG. 1) are the same components as those of the star sensor 10 (FIG. 1), and thus description thereof will be omitted. Hereinafter, the calculation unit 701 of the star sensor 70 will be described. The operation unit 701 is a hardware operation unit provided between the image input unit 101 and the memory interface unit 104 and including an adder, a multiplier, and the like. The calculation unit 701 receives the image data and the clock from the image input unit 101, and performs a calculation in real time.
When the operation is completed for a predetermined amount of data, the operation unit 701 outputs the operation value to the memory interface unit 104. At this time, an image input clock (not shown) is also output at the same time. The operation performed here is an operation that should be performed by the MPU after it is originally stored in the memory.

As described above, according to the fourth embodiment, by providing the arithmetic unit as a hardware arithmetic unit, M
A part of the processing performed by the PU 107 is previously performed by the arithmetic unit 701
Is performed, the load on the MPU 107 decreases,
The data processing speed of U107 is improved.

[0037]

According to the present invention, the arbitration unit has the bus arbitration function of occupying the bus right for a minimum time required for reading and writing to the memory and transferring the bus right to the central processing unit at other times. Thus, the delay in data processing can be reduced. In addition, since data is stored in a single memory, the number of components can be reduced and cost can be reduced, and the reliability is improved because the number of components is small. Here, a data input / output unit for accessing a single memory includes an image input unit for inputting image data of a star as data, a reception command input unit for receiving a command from the ground and inputting the data, and a telemetry. Since at least one of the obtained telemetry data is read from the memory as data and output toward the ground, the above-described effects can be obtained with respect to data necessary for the onboard satellite star sensor.

Further, even if the output from the data input / output unit is data of different types such as image data and commands, the arbitration unit can recognize the occupation of the bus by the data output unit based only on the control signal.

Also, more data (for example,
Image data, commands) can be stored in the memory, and more telemetry can be read out. As a result, the time required for the central processing unit to access the memory increases, and the delay in the processing speed of the central processing unit due to the data bus arbitration function can be reduced.

In a star sensor for on-board satellite that requires only a star image larger than the threshold value, only the image larger than the threshold value is stored in the memory, so that all the images are stored in the memory. The efficiency of data processing can be improved.

Since a predetermined operation is performed in advance before storing in the memory and the operation value is stored in the memory, the load on the central processing unit is reduced, and the data processing speed of the central processing unit is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a star sensor according to a first embodiment.

FIG. 2 is a timing chart of signals transmitted and received by a star sensor.

FIG. 3 is a block diagram illustrating a configuration of a star sensor according to a second embodiment.

FIG. 4 is a block diagram illustrating a data storage unit of an arbitration unit.

FIG. 5 is a timing chart showing the operation of the arbitration unit.

FIG. 6 is a block diagram illustrating a configuration of a star sensor according to a third embodiment.

FIG. 7 is a block diagram illustrating a configuration of a star sensor according to a fourth embodiment.

[Explanation of symbols]

10 star sensor, 101 image input unit, 102
Receiving command input unit, 103 telemetry transmitting unit,
104 memory interface unit, 105 arbitration unit,
106 memory, 107 MPU

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Haruhiko Shimo 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) in Mitsubishi Electric Corporation 5B060 CD17 KA03

Claims (5)

[Claims] 1. A star sensor mounted on a satellite, comprising: a bus; a single memory connected to the bus for storing data; and a memory connected to the bus and accessing the memory for inputting and outputting the data. A data input / output unit for inputting stellar image data as the data, a reception command input unit for receiving a command from the ground and inputting the data as the data, and data obtained by telemetry. A data input / output unit which is at least one of a telemetry transmission unit for reading telemetry from the memory as the data and outputting the data toward the ground; and a central unit connected to a bus for controlling a satellite using the data input to the memory. A processing unit and an arbitration unit for arbitrating bus occupation, wherein the data input / output unit occupies the bus only while the data input / output unit accesses the memory. Because, star sensor data input-output unit is provided with an arbitration unit to return the occupation of the bus to the central processing unit upon completion of the access to the memory. 2. An arbitration unit further comprising: a memory interface unit that receives a clock for inputting / outputting the data from a data input / output unit, and outputs a control signal for requesting occupation of a bus to the arbitration unit. 2. The star sensor according to claim 1, wherein the data output unit recognizes the occupation of the bus based on the control signal output from the unit. 3. A first bus for connecting a memory and an arbitration unit.
Is larger than the second bus width of the bus connecting the data input / output unit and the arbitration unit. The arbitration unit receives the data from the data input / output unit, accumulates the data by a predetermined amount, and outputs the data to the memory. 3. The star sensor according to claim 2, wherein the data read from the memory is output to the data input / output unit according to the second bus width. 4. 4. When the data is image data, the image processing apparatus further comprises a comparing unit that compares a threshold value with the size of the image data and outputs a comparison result. The star sensor according to claim 2, wherein it is determined whether or not the input / output unit is allowed to occupy the bus. 5. The image processing apparatus according to claim 2, further comprising an operation unit that receives the image data and performs an operation for controlling a satellite instead of a central control unit when the data is image data.
2. The star sensor according to 1.