NASA Scientific and Technical Aerospace Reports

20040074264 NASA Goddard Space Flight Center, Greenbelt, MD, USA
A Continuous Adiabatic Demagnetization Refrigerator for Far-IR/Sub-mm Astronomy
Shirron, Peter; Canavan, Edgar; DiPirro, Michael; Jackson, Michael; King, Todd; Tuttle, James; New Concepts for
Far-Infrared and Submillimeter Space Astronomy; April 2004, pp. 454-460; In English; See also 20040074260; No
Copyright; Avail: CASI; A02, Hardcopy
We report on recent progress in the development of a continuous adiabatic demagnetization refrigerator (CADR).
Continuous operation avoids the constraints of long hold times and short recycle times that lead to the generally large mass
of single-shot ADRs, allowing us to achieve an order of magnitude larger cooling power per unit mass. Our current design
goal is 10 microW of cooling at 50 mK using a 6-10 K heat sink. The estimated mass is less than 10 kg, including magnetic
shielding of each stage. The relatively high heat rejection capability allows it to operate with a mechanical cryocooler as part
of a cryogen-free, low temperature cooling system. This has the advantages of long mission life and reduced complexity and
cost. We have assembled a three-stage CADR and have demonstrated continuous cooling using a superfluid helium bath as
the heat sink. The temperature stability is 8 microK rms or better over the entire cycle, and the cooling power is 2.5 microW
at 60 mK rising to 10 microW at 100 mK.
Author
Adiabatic Conditions; Demagnetization; Refrigerators; Cryogenic Cooling; Infrared Astronomy
20040074276 NASA Goddard Space Flight Center, Greenbelt, MD, USA
Cryo-Infrared Optical Characterization at NASA GSFC
Boucarut, Ray; Quijada, Manuel A.; Henry, Ross M.; New Concepts for Far-Infrared and Submillimeter Space Astronomy;
April 2004, pp. 428-437; In English; See also 20040074260; No Copyright; Avail: CASI; A02, Hardcopy
The development of large space infrared optical systems, such as the Next Generation Space Telescope (NGST), has
increased requirements for measurement accuracy in the optical properties of materials. Many materials used as optical
components in infrared optical systems, have strong temperature dependence in their optical properties. Unfortunately, data
on the temperature dependence of most of these materials is sparse. In this paper, we provide a description of the capabilities
existing in the Optics Branch at the Goddard Space Flight Center that enable the characterization of the refractive index and
absorption coefficient changes and other optical properties in infrared materials at cryogenic temperatures. Details of the
experimental apparatus, which include continuous flow liquid helium optical cryostat, and a Fourier Transform Infrared
(FTIR) spectrometer are discussed.
Author
Cryogenics; Optical Equipment; Optical Properties; Infrared Spectrometers
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COMMUNICATIONS AND RADAR
Includes radar; radio, wire, and optical communications; land and global communications; communications theory. For related
information see also 04 Aircraft Communications and Navigation; and 17 Space Communications, Spacecraft Communications,
Command and Tracking; for search and rescue, see 03 Air Transportation and Safety; and 16 Space Transportation and Safety.
20040068233 Federal Trade Commission, Washington, DC, USA
False Claims in SPAM. A Report by the FTC’s Division of Marketing Practices
Apr. 30, 2003; In English
Report No.(s): PB2004-103731; No Copyright; Avail: National Technical Information Service (NTIS)
In this report, staff of the Federal Trade Commission’s (’FTC’) Division of Marketing Practices describes the results of
its review of approximately 1,000 pieces of unsolicited commercial email (UCE), commonly known as ‘spam.’ This random
sample was drawn from a pool of over 11,000,000 pieces of spam. This study, which focuses on the likely truth or falsity of
claims contained in the messages, supplements two previous FTC studies of spam - the ‘Spam Harvest’ (finding that 86% of
addresses posted to web pages and newsgroups received spam) and the ‘Remove Me Surf’ (finding that 63% of email list
removal requests were not honored). This study represents the first extensive review of false claims appearing in UCE.
NTIS
Electronic Mail; World Wide Web; Information Dissemination
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