What are two devices attached to weather balloons?

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Tags

1. #radiosonde
2. #sounding
3. #aloft
4. #called
5. #speed
6. #balloon
7. #measuring
8. #instruments
9. #expendable
10. #means
11. #weather
12. #information
13. #pressure
14. #temperature
15. #altitude
16. #small
17. #humidity
18. #atmospheric
19. #specifically
20. #device
21. #carries