JP2937167B2 - Environmental condition measuring apparatus and method for artificial satellite onboard equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a space-borne device mounted on a satellite or the like, and relates to an environment for a space-borne device for measuring pressure in a sealed container for a certain purpose in space. The present invention relates to a condition measuring device and a measuring method.

[0002]

2. Description of the Related Art In the prior art, although not limited to artificial satellites, the main variable element of the output characteristics of a pressure sensor element is amplified by two sensors and the output value from each sensor is amplified. After the signal is amplified by the means, the signal is stored in an appropriate storage means, a difference value between the output values of the two is obtained, and a signal processing method for canceling the offset of the amplification means is disclosed in, for example, JP-A-2-222809. It is disclosed in the gazette.

That is, in this conventional example, the fluctuation of the differential output (31 and 41) of the pressure sensor due to the temperature is caused by the use of the resistor, that is, the resistor 35 used to fix the gain of the operational amplifier. 36 and 45. As another example, there is no suggestion regarding application in outer space as in the above-described conventional example, but as disclosed in, for example, JP-A-7-212139,
There is known a method of arbitrarily setting a change amount and a change direction of the offset voltage with respect to a temperature change by appropriately setting a ratio of the resistance values of the variable resistors VR2 and VR3 to the pressure sensor 1.

In addition, in consideration of the conventional technology for space equipment, generally, the temperature environment for the equipment is severe, so that temperature drift is likely to occur, and the device is likely to be deteriorated by the influence of radiation. There is a restriction that maintenance is not possible when deterioration occurs.
Furthermore, in the observation and detection operations by artificial satellites in such a space, if the above-mentioned problems or these elements are duplicated, measured values obtained on the ground side (by wireless communication) It is difficult to obtain an accurate output by correctly canceling the drift value from the satellite signal (transmitted from a satellite), so that only a measurement value inferior to the accuracy of the original device has been obtained.

[0005]

A first problem with the prior art described above is that the variable resistors used to compensate for temperature are useful for equipment typically used on the ground, This does not apply to satellite-borne devices that are required to be used in a space environment. The reason is that satellite-borne equipment is generally not maintainable,
In addition, in order to perform on-orbit compensation, this control is performed remotely, which entails enlargement of the apparatus and complicated operation.

A second problem is that, in the above-mentioned prior art, in addition to the temperature compensation, when the deterioration of the sensor or the like and the characteristic fluctuation due to radiation affect the sensor and the sensor output processing circuit. Not considered at all. The reason for this is that, in the prior art, no consideration is given to the use of sensors and the like in outer space, and accordingly, measures against degradation and aging of the above sensors and the like in outer space are not taken into account. There is no disclosure at all, and the amount of characteristic fluctuation of sensors and the like due to radiation in space and the amount of characteristic fluctuation due to aging cannot be easily predicted before the device operates in orbit in space. For this reason, temporarily
Even if this is performed by adjusting the resistance value, it is difficult to make an appropriate adjustment because prediction is impossible.

Accordingly, an object of the present invention is to improve the above-mentioned drawbacks of the prior art, and to improve the environmental conditions in a closed container containing various measuring devices or observation devices used as equipment for mounting on artificial satellites. The change is monitored using an appropriate measurement system, and in a control system for constantly maintaining the environmental conditions in the container in the closed container at a predetermined environmental condition, the temperature is measured in the measurement system. To provide an environmental condition measuring device for artificial satellites that can always obtain correct measurement values by canceling fluctuations of measurement values due to drift, deterioration of characteristics of sensors etc. due to radiation, and fluctuations of measurement values due to aging deterioration. Aim.

In addition, since the predetermined device mounted on the artificial satellite starts operating in orbit, the operability of adjusting the output of the measurement system depending on the environment to which the device is exposed is prevented from becoming complicated. An object of the present invention is to provide an environmental condition measuring device capable of realizing this with a simple circuit configuration.

[0009]

The present invention basically employs the following technical configuration in order to achieve the above object. That is, as a first aspect of the present invention, in a system for monitoring environmental conditions in a container of a closed container mounted on an artificial satellite, a first sensor for measuring environmental conditions in the container of the closed container, A second sensor for measuring an environmental condition outside the container of the closed container is provided in a part of the closed container, and an output of each of the first and second sensors simultaneously output from each of the first and second sensors is provided. An environmental condition measuring device for an artificial satellite-equipped device provided with arithmetic means for calculating a difference. As a second aspect according to the present invention, an environmental condition in a closed container mounted on an artificial satellite is monitored. A first sensor provided in a part of the closed container for measuring environmental conditions inside the container of the closed container, and a second sensor for measuring environmental conditions outside the container of the closed container. And from each at the same time By calculating the difference between the two output values using the individual output values that are input, fluctuations due to temperature changes in the sensor characteristics, deterioration of characteristics due to radiation, fluctuations in output values due to aging, etc. This is a method for measuring environmental conditions for an artificial satellite-mounted device that cancels a drift amount included in an output value caused by the above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The environmental condition measuring apparatus and the environmental condition measuring method for a device mounted on a satellite according to the present invention adopt the above-mentioned technical configuration. When the environmental condition measuring sensor detects the pressure, the sensor has two pressure sensors having the same or different characteristics. Absolute vacuum)
Are measured simultaneously. And by obtaining the difference,
A sensor that measures the pressure in a sealed container with higher accuracy by canceling factors that vary depending on the environment to which the pressure sensor is exposed in space, that is, temperature drift, output drift due to radiation deterioration and aging deterioration, etc. It is.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete example of an environmental condition measuring apparatus for an onboard artificial satellite according to the present invention will be described below in detail with reference to the drawings. That is, FIG. 1 is a cross-sectional view showing a configuration of a specific example of an environmental condition measuring device for an artificial satellite mounted device according to the present invention. In FIG. In the monitoring system, the closed container 1
A first sensor 4 for measuring environmental conditions inside the container and a second sensor 5 for measuring environmental conditions outside the container of the closed container 1 are provided in a part of the closed container 1, and Environmental condition measuring device for artificial satellite-equipped equipment 25 provided with arithmetic means 26 for calculating the difference between individual output values simultaneously output from each of first and second sensors 4 and 5.
It is shown.

That is, in the present invention, as described above,
Measurement in which a predetermined observation device, a measurement device, and the like are installed in a sealed container 1 set to environmental conditions in the container maintained at a predetermined temperature or a predetermined pressure mounted on the artificial satellite 30,
In the observation system, the inside of the sealed container 1 must be constantly maintained at a constant environmental condition in the container so that the observation device, the measurement device, and the like perform normal observation and measurement operations. The environmental conditions in the container in the closed container 1 are always accurately and precisely measured, and if a change occurs, the adjustment operation is immediately performed to return to the predetermined environmental conditions in the container. Is required.

However, in the outer space, it is not possible to perform the adjustment operation easily and easily as on the ground. Even if the adjusting means specially provided to the artificial satellite 30 is driven to restore the environmental conditions in the container, the complicated adjusting means must be separately mounted on the artificial satellite 30, and the weight increases. In addition to the increase in the number of causes of failure, there is also a problem that the cost is increased.

Of course, as described as a problem of the prior art, the radiation, impact,
It is impossible to predict at all how the sensor or the like will be degraded while exhibiting the behavior due to the influence of temperature or the like. It was also impossible to adjust the output of the sensor based on this. Therefore, in the present invention, a means for obtaining accurate reference data that can be used even in outer space is provided,
Using the reference data, the drift due to the change in temperature included in the output value from the sensor, or the deterioration due to radiation or the like in the characteristics of the sensor, and the drift generated due to the deterioration due to aging. ,
In other words, by correcting so as to cancel the offset, it is possible to accurately detect the environmental conditions in the container.

Accordingly, the environmental condition measuring apparatus 30 for an artificial satellite-mounted device according to the present invention has a simple mechanism, has few elements of failure, is easy to control, and can reduce the cost, and its environment. A condition measurement method is provided. The environmental conditions in the container according to the present invention may be, for example, the pressure in the closed container 1 or the temperature.

Further, in the present invention, the first sensor 4 and the second sensor 5 are attached to a part of the wall of the closed container 1, and the first sensor 4 is , The sensor sensing part, that is, the detection end 6,
And the other components of the first sensor 4 are protruded from the wall of the closed container 1 to the outside, that is, between the housing of the artificial satellite 30 of the closed container 1. .

On the other hand, the second sensor 5 has its sensor sensing portion, that is, the detection end 7, provided outside the closed container 1, and the other components of the second sensor 5 are connected to the closed sensor 1. It protrudes inside the container 1. In this specific example, when the sensors 4 and 5 are sensors that detect pressure, the second sensor 5
However, since it is configured to detect a space having substantially the same degree of absolute vacuum as outer space, it functions as a reference data output sensor.

When the sensors 4 and 5 are sensors for detecting a temperature, the second sensor 5 is desirably engaged with or opposed to means for generating an appropriate reference temperature. . The first sensor and the second sensor according to the present invention are arranged in the same panel 40 made of a material such as aluminum, for example, as shown in FIG. Is the closed container 1
Attached to a part of the side wall.

As is apparent from FIG. 2, the detection ends 6, 7 of the first sensor 4 and the second sensor 5 are mounted so as to be arranged on different surfaces of the panel 40, respectively. Therefore, when the panel 40 is attached to the side wall of the closed container 1, the detection end 6 of the first sensor 4 is located in the closed container 1 as shown in FIG. In addition, the detection end 7 of the second sensor 5 is located outside the closed container 1.

In the present invention, the first sensor 4 and the second sensor 5 may have the same detection sensitivity or different sensitivities. good. As can be understood from the above description, in the environmental condition measuring device 25 for mounting on a satellite according to the present invention, basically, two sensors having the same characteristics are attached to the same flange, and the sensors having the same characteristics are mounted. Expose to the environment. For this reason,
The two sensors produce the same temperature drift at the same time,
Equivalent radiation deterioration and output change due to aging deterioration occur.

The object to be measured is any environmental condition in the container in the closed container. When the environmental condition in the container is the pressure in the closed container, the measurement by the other space-side sensor is always absolute vacuum ( (Ie, known pressure) is measured, so by using this as a reference value,
It is possible to know the drift amount of the output characteristic that can change depending on the environment to which the pressure sensor is exposed in space orbit.

Therefore, a more accurate measurement can be performed by always canceling this drift amount from the pressure sensor that measures the object to be measured. Next, in a specific example of the environmental condition measuring device 25 mounted on a satellite according to the present invention, the configuration and operation of the case where pressure is detected as the environmental condition in the container will be described in more detail with reference to the drawings. explain.

FIG. 1 shows a sealed container 1 mounted on an artificial satellite 30 or the like. What purpose the closed container 1 is used for or the purpose thereof does not matter here. The constituent material of the closed container is also usually formed of aluminum, but it does not matter here. As is clear from FIGS. 1 and 2, a panel 40 held by the sensor mounting flange 2 has a pressure sensor 4, that is, a first sensor 4 for measuring inside the container, and a pressure sensor 4 for measuring outside the container. Sensor 5, ie the second
Are mounted respectively.

The material of the flange is preferably a material having good thermal conductivity so that the thermal environment of each sensor is as equal as possible. In the example of FIG. 1, the arrangement of the signal output end of the pressure sensor corresponds to the sensing unit 6 that is the detection end with respect to the panel 40.
In this case, the wiring of the pressure sensor 5 is connected to the hermetic shield connector 3.
And the wiring of the pressure sensor 4 and the arithmetic means 26 which is a sensor signal processing unit.

FIG. 2 shows a specific example of the sensor mounting flange 2 and the panel 40. In the example of FIG. 2, a flange for attaching the sensor to the closed container 1 is shown.
Here, the pressure sensor is a sensor having a shape in which the sensing portion is screwed into a hole formed in the panel 40 held by the flange. The flange 2 and the panel 40 are joined via an O-ring 8 to suppress leakage after the flange 2 is attached to a closed container.

Further, as shown in FIG. 4, the pressure sensors mounted in two opposite directions measure the internal pressure of the sealed container 1 in the satellite 30 at the pressure sensor measuring point 18 and the external pressure is measured by the pressure sensor. It measures at the measurement point 19. Here, the external pressure indicates the pressure in the outer space, and is generally an absolute vacuum measurement of 1 × 10 ⁻⁸ Torr or less.
FIG. 3 is a block diagram showing a specific example of the output signal circuit of the pressure sensor.

The configuration of the first sensor 4 and the second sensor 5 used in the present invention is not particularly specified. For example, a strain gauge type using a diaphragm or a piezoelectric A strain gauge type using an element can be used. FIG. 3 shows an example in which a strain gauge type using a diaphragm is used.

That is, for example, a diaphragm 12 constituting the first sensor 4 and a diaphragm 13 constituting the second sensor 5 are provided, and a constant power supply circuit 11 supplies a constant power to each of the diaphragms 12, 13. Supply voltage. Each sensor output is amplified by amplifier circuits 14 and 15, and the difference is obtained by a difference value output circuit 16 for calculating and processing the difference between the output values of the two sensors constituted by the amplifier circuits. Analog / digital conversion circuit 17
Output via.

The difference value output circuit 16 and the analog / digital conversion circuit 17 in FIG.
6. The measurement value data of the environmental condition in the container output from the arithmetic means 26 is transmitted to the ground station via the telemetry collection circuit 20 and the appropriate transmission means 21 as necessary.

Next, the operation in the above specific example will be described in detail with reference to FIG. That is, a constant voltage V is supplied from the common power supply circuit 11 to the diaphragm 12 and the diaphragm 13 of the two pressure sensors attached to the flange so as to be exposed to the same environment. Diaphragm 12 measures the pressure in the closed vessel,
3 measures the pressure in outer space (absolute vacuum).

As a result, the diaphragm 12 has an arbitrary pressure.
Output voltage V₁Is output. Also die
The diaphragm 13 causes almost no distortion due to the absolute vacuum.
For V ₁Smaller value V_TwoIs output. V₁And V_Two
Is the temperature drift characteristic, radiation,
Common drift amount V from deterioration due to year_dContains.

The output V ₂ of the diaphragm 13 for measuring the absolute vacuum ideally shows 0 V, but V ₂ ≒ V _d because of the above-mentioned drift. Further, each of the diaphragms V ₁ and V ₂ is amplified by the amplifier circuits 14 and 15. Variations in the characteristics of the individual pressure sensors (variations in the outputs of the diaphragms 12 and 13)
The correction can be made by setting the amplification factors of (15) and (15).

In the amplifier circuit 16 which is a difference value calculating means,
When determining the difference between the output of each of the _{diaphragm, V 1 -V 2 = (V} 1 + V d) -V d = V 1 becomes, V ₁ is the value excluding the drift amount V _d from the pressure measurements in the closed container Therefore, it indicates a value corresponding to the current accurate pressure measurement value of the closed container 1.

This is digitized by an A / D conversion circuit 17 and transmitted to a ground station via a telemetry collection circuit 20 and a transmitter 21 unique to each artificial satellite. The ground station receives V ₁
Using the (digital value) calibration table, the pressure inside the closed vessel on the orbit is converted and found. That is, the basic configuration of the environmental condition measuring method for mounting on a satellite according to the present invention includes a pressure sensor 4 for measuring the pressure inside a closed container mounted for some purpose on a satellite or the like, Pressure sensor 5 for measuring the space side to cancel the fluctuation of the sensor characteristics due to temperature drift and radiation of the same, and the same flange and pressure sensor for mounting the pressure sensor 4 and the pressure sensor 5 to promote the same fluctuation of the characteristics After amplifying the measurement output data of the pressure sensor 4 and the pressure sensor 5, the measured value of the absolute pressure with respect to the outer space (absolute vacuum) is obtained by the circuit for obtaining the difference.

Regarding the above specific example, it is assumed that in FIG. 1, the closed container 1 is a container of 1000 cm ³ and the internal pressure is maintained at 1 Torr. The pressure sensor 4 serving as the first sensor and the pressure sensor 5 serving as the second sensor are both selected to have the same measurement sensitivity, exhibit 0.1 V in the full range of measurement 10 Torr, and exhibit a temperature drift of 0.1 V. A small strain gauge pressure sensor of 01 Torr / ° C could be used.

If the temperature to which the closed container 1 is exposed on the track is -30 ° C. to + 40 ° C., the maximum value of the temperature change ΔT = 70 ° C. Drift is 0.01 × 70 = 0.7To at the maximum
rr. Here, for example, consider a case where the temperature of the closed container changes from 0 ° C. to 20 ° C. on the track.

FIG. 5 is a PV characteristic graph showing the relationship between the general degree of vacuum of the pressure sensors 4 and 5 and the output voltage of the sensors. That is, at 20 ° C., the pressure sensor 4 measures 1 Torr and shows an output V ₁ = 0.01 V. At this time, the pressure sensor 5 measuring the absolute vacuum shows an output V ₂ = 0V. The temperature environment of the sealed container 1 changes to 0 ° C
, The pressure sensor 4 indicates V ₁ ′ = 0.012 V due to temperature drift. Similarly, V ₂ ′ = 0.
002V. As described above, V ₂ ′
≒ V _d , that is, the amount of temperature drift, V ₁ ′ −V ₂ ′ = 0.012-0.002 = 0.01 V
It is.

FIG. 5 shows an example in which the output of the pressure sensor shows an ideal straight line having no drift at 20 ° C. Therefore, the output voltage characteristic at 20 ° C. may be considered as a reference. V ₁ '-V ₂ ' excluding
If 0.01 V can be known, the drift component due to the temperature change can be grasped as a canceled value without considering the temperature change. Therefore, it is calculated from this voltage output value that the pressure in the container 1 is 1 Torr. I can do it.

Factors other than temperature drift (radiation deterioration, aging deterioration) can be canceled in the same manner. That is, in the above specific example, when the temperature to which the pressure sensors 4 and 5 are exposed is 20 ° C., the output voltage V ₁ of the diaphragm 12 shows V ₁ = 0.01 V, as is clear from the graph of FIG. . On the other hand, the output voltage V ₂ of the diaphragm 13 is V ₂ = 0.
V.

Amplification rate α of amplifier circuits 14 and 15 = 10
Then, the differential input voltage value of the amplifier circuit 16 is V ₁ ′
= 0.01 × 10 = 0.1V, and V ₂ ′ = 0 × 10 =
Is 0V, the differential output is _{V 1 '-V 2' = 0.1V} . Therefore, if the weighting of data in the A / D conversion circuit 17 is 1 bit full scale of 8 bits, 1 digit = 3.9 mV, and 16 bits for an input of 0.1 V
Outputs (19) _HEX with the value expressed in the decimal system. This value is sent to the ground station.

On the other hand, even when the temperature to which the pressure sensors 4 and 5 are exposed is 0 ° C., as described above, the differential input of the amplifier circuit 16 is 0.1 V and is not affected by the temperature.
(19) _HEX can be transmitted. Next, as another specific example of the present invention, a case where the two pressure sensors 4 and 5 used in the specific example do not have equivalent characteristics will be described.

That is, in FIG. 3, since the diaphragm 13 measures the absolute vacuum, it is desirable that the selection of the full range (selection of the type of the pressure sensor) be low, for example, a case where the full range is 0.1 V and 10 Torr. And the pressure measured by the diaphragm 12 is 1
When a relatively high pressure such as an atmospheric pressure (= 270 Torr) is targeted, the full range must be adjusted to the range of the pressure to be measured.
It is desirable to use one of 00 Torr.

In such a case, the diaphragms 12 and 1
Third, it is possible to select sensors having different characteristics.
In such a case, as in the first embodiment, a sensor having a sensitivity of 10 Torr in a full range of 0.1 V and a temperature drift of 0.01 Torr / ° C. is used as the diaphragm 13. To perform measurement, 100 To in full range 0.1V
Consider a case where a sensor having sensitivity of rr and temperature drift of 0.02 Torr / ° C. is used.

Also in this case, the absolute vacuum is measured by the diaphragm 13 on the orbit, and the temperature change indicates that the output of V ₂ changes from 0 V to 0.002 V when the temperature changes from 20 ° C. to 0 ° C. Will show that it has changed. On the other hand, for the diaphragm 12, a change from 20 ° C. to 0 ° C. corresponds to a drift of 0.02 Torr × 20 = 0.4 Torr and an output voltage of 0.4 mV.

Therefore, in the amplification circuit 15 in this case, by giving a value of 0.4 mV / 2 mV = 0.2 as the amplification factor, the temperature drift of the diaphragm 12 by 20 ° C. change can be canceled. That is, the method for measuring the environmental conditions for mounting on a satellite according to the present invention includes, in a system for monitoring environmental conditions in a container of a closed container mounted on a satellite, the method provided on a part of the closed container. By using individual output values simultaneously output from the first sensor for measuring the environmental conditions inside the container of the closed container and the second sensor for measuring the environmental conditions outside the container of the closed container, This is an environmental condition measuring method for an onboard artificial satellite device in which a difference between both output values is obtained to cancel a deterioration in the sensor characteristics and a drift included in the output value due to a change with time.

[0046]

The first embodiment of the present invention employs the technical configuration as described above, since the environmental condition measuring device for mounting on a satellite and the environmental condition measuring method for mounting on a satellite according to the present invention have the following advantages. In addition, it is possible to cancel fluctuations in measured values due to temperature drift, radiation deterioration, and aging deterioration of a sensor used in a measurement system for environmental conditions in a container mounted on an artificial satellite or the like. This enables more accurate measurement.

The reason is that, for example, an absolute vacuum in the outer space can be measured by a sensor having the same characteristics to obtain a drift amount.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a specific example of an environmental condition measuring device for mounting on a satellite according to the present invention.

FIG. 2 is a perspective view showing an example of the structure of a sensor mounting panel used in the environmental condition measuring device for mounting on a satellite according to the present invention.

FIG. 3 is a block diagram showing an example of a measurement data processing circuit used in a specific example of the environmental condition measuring device mounted on an artificial satellite according to the present invention.

FIG. 4 is a schematic diagram showing the inside of a satellite, showing an embodiment of the present invention.

FIG. 5 is an output characteristic graph of a pressure sensor used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Airtight container 2 ... Sensor mounting flange 3 ... Hermetic shield connector 4 ... 1st sensor 5 ... 2nd sensor 6, 7 ... Detection end part, sensor sensing part 8 ... O-ring 9 ... 10 ... Pressure sensor lead wire 11 ... Power supply circuit 12, 13 ... Diaphragm 14, 15 ... Amplifier circuit 16 ... Difference value calculation circuit 17 ... A / D conversion circuit 18, 19 ... Pressure sensor measurement point 20 ... Telemetry collection circuit 21 ... Transmitter 25 ... Environmental condition measuring device 26 ... Calculation means 30 ... Satellite 40 ... Panel

Claims (11)

(57) [Claims] 1. A system for monitoring environmental conditions in a closed vessel mounted on an artificial satellite, comprising: a first sensor for measuring an environmental condition in the closed vessel of the closed vessel; A second sensor for measuring environmental conditions is provided on a part of the closed container, and the first and second sensors are provided.
An environmental condition measuring device for a device mounted on a satellite, characterized by comprising a calculating means for calculating a difference between individual output values simultaneously output from the respective sensors. 2. The apparatus according to claim 1, wherein the environmental condition in the container is a pressure or a temperature in the closed container. 3. A difference value between an output value of the first sensor and an output value of the second sensor output from the calculating means is a drift due to a temperature change in the sensor characteristic or a radiation in the sensor characteristic. 3. The environmental condition measuring apparatus according to claim 1 or 2, wherein a value obtained by canceling a drift due to deterioration and aging with respect to the time is displayed. 4. The environmental condition for a satellite-mounted device according to claim 1, wherein said first sensor and said second sensor have the same sensitivity to each other. Measuring device. 5. The environmental condition measuring device according to claim 1, wherein said first sensor and said second sensor have different sensitivities. apparatus. 6. The first sensor and the second sensor are arranged in the same panel, and the panel is attached to a part of a side wall of the closed container. The environmental condition measuring device for an onboard artificial satellite device according to claim 1. 7. The panel according to claim 6, wherein the detection terminals of the first sensor and the second sensor are individually arranged on different main surfaces of the panel.
The environmental condition measuring device for an onboard artificial satellite device described in the above. 8. A system for monitoring environmental conditions in a closed container mounted on an artificial satellite, wherein a first environmental condition provided in a part of the closed container, which is provided in a part of the closed container, is measured. By using the individual output values simultaneously output from each of the sensor and the second sensor for measuring the environmental conditions outside the container of the closed container, the difference between the two output values is obtained, A method for measuring environmental conditions for a satellite-mounted device, comprising: canceling a drift due to a temperature change in characteristics, a deterioration due to radiation or the like in the sensor characteristics, and a drift component included in an output value due to a temporal change. 9. The method according to claim 8, wherein the environmental condition in the container is a pressure or a temperature in the closed container. 10. The method according to claim 8, wherein the first sensor and the second sensor have the same sensitivity. 11. The method according to claim 8, wherein the first sensor and the second sensor have different sensitivities from each other.