The role and contributions of Frank McDonald in extending high energy astrophysics to the sub-eV photon energy range (in putting infrared astronomy into orbit) are discussed

Hauser, Michael G.

English

NASA Technical Reports Server

N87- 24264
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INFRARED ASTRONOMY
Michael G. Hauser
Laboratory for Extraterrestrial Physics
Goddard Space Flight Center
Greenbelt, Maryland 20771
1. INFRARED ASTRONOMY
One of the lesser known contributions of Frank McDonald to space science
is his role in extending high energy astrophysics to the sub-eV photon energy
range--in putting infrared astronomy into orbit. This seemingly paradoxical
extension was, in fact, both reasonable and timely. Reasonable, because so
many infrared photons emanate from highly energetic sources such as star-
forming clouds, active galaxies and the Big Bang itself. Though each photon
carries modest energy, one must measure the infrared brightness to be able
to understand overall source energetics. Timely, because the technical ingre-
dients needed to make infrared space astronomy a reality, including propul-
sion, attitude control, cooling, and sensors, were either in hand or at least
within reach.
In the spring of 1974 I was working at Caltech on new detector technology
for far-infrared astronomy. I had the good fortune of having lunch one day
with Len Fisk, then a member of McDonald's High Energy Astrophysics Divi-
sion at Goddard. Len mentioned that Frank was thinking that it was time
to start a serious effort leading toward space astronomy in the infrared, and
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suggestedthat I contactFrank if that would interestme. I arrivedat God-
dardlate in the summerto takeup thechallenge,buoyedsubstantiallyby
my confidencein Frank'ssupportandjudgment,alreadywell-confirmedin
numerousotherdisciplines.
In additionto enthusiasmandmoralsupport,Frankbestoweduponhisfledg-
ling effort severalindispensibleingredients:talented,highlymotivatedpeo-
ple, in this casethree individualsfrom other parts of his Division (Bob
Silverberg,just completinghisPh.D. researchoncosmicrays;DaveWalser,
anexperiencedtechnicianaboutto completehiselectricalengineeringdegree;
andTonyFlanick,theseniortechnicianin thelowenergycosmicraygroup);
fundsto beginequippingalaboratoryanddevelopinghardware(I neverasked
himwhoseaccounthespiritedthis from);andspacefor our laboratory(those
whohavenot workedin Building2 cannotappreciatethe magnanimityof
thiscontribution).In hisquiet,unobtrusivewayFrankofferedmuchvaluable
advice,rangingfrom whomto contactat Goddardor Headquartersto make
thingshappen(heimmediatelyput us in contactwith Pat Thaddeusat the
GoddardInstitutefor SpaceStudies(GISS),with whomwehavehadfruitful
collaborationto thisday),to howto makerecruitingdecisions(puttalentand
qualityof workabovespecializedexperience).Finally,of course,heprovided
a stimulatingandfertilework environment,characterizedby theintellectual
fervorof themanyresearchgroupswithoverlappingscientificinterests,solid
engineeringandsoftwaresupport,andunflaggingmanagementencourage-
mentwith minimal bureaucraticdistraction.
That Frank'sjudgmentwasimpeccableasto theproper timing for pursuit
of infraredastronomyfrom spaceisborneout bythesubsequentrecord.By
thetimeI arrivedat Goddard,NASAhadannouncedanopportunityto pro-
poseExplorer-classmissionsor missionconceptstudies,whichturnedout to
be theonly suchopportunityin thenextdozenyears.At that time, the in-
fraredskywaslittle knownat wavelengthslongerthan20microns,andwas
unobservedonspatialscaleslargerthantensof arc-minutesat anywavelength
becauseof thebright atmosphericemission.At the longwavelengthendof
the infraredspectrum,therewasintensecosmologicalinterestin measuring
theshapeof thecosmicbackgroundradiationspectrum,thenfirmlyestablished
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onlyon theRayleigh-Jeanssideof thepresumed 3 K spectrum, and in deter-
mining the anisotropy of that radiation.
With Frank's support and guidance we generated two proposals within a few
months: one to conduct a sensitive sky survey at 50 and 100 microns, and
the second, initiated by Pat Thaddeus and John Mather, then a young post-
doc at GISS, to build a Cosmic Background Radiation Satellite to make
definitive measurements of the microwave background and search for a
primeval infrared background component. The latter included as collaborators
David Wilkinson from Princeton and Rainer Weiss from MIT. In retrospect,
these proposals were very much on target scientifically, but were programma-
tically remarkably naive (for example, we seriously discussed building the entire
instrument complement for the cosmic background mission, including the
dewar, for five million dollars!). Fortunately, the estimates became more credi-
ble, the scientific promise prevailed in the evaluation process, and the first
proposal led to our participation in the Infrared Astronomical Satellite (IRAS)
mission, while the second, though via a more protracted path, led to the Cosmic
Background Explorer (COBE). We were suddenly caught up in the process
of opening a new window on the universe, and in probing its most ancient
radiative relics!
The road to completion of space programs is a lengthy one, and these two
in particular have redefined the meaning of Explorer-class missions. With the
wisdom of experience, and perhaps a bit of prescience, Frank from the outset
encouraged us also to pursue programs which would provide both short-term
scientific return and opportunities to test new technology germane to the space
business. Our first such endeavor, also begun in the fall of 1974, was develop-
ment of a balloon-borne telescope and submillimeter photometer for investiga-
tion of the large-scale luminosity and interstellar mass distributions in the galac-
tic plane. With pointing control and maneuvering requirements substantially
tougher than those of previous balloon payloads developed in Frank's lab,
we presented a significant challenge to his engineering staff, as he no doubt
wished. Their able contributions, along with those of several other engineer-
ing groups at Goddard, resulted in a payload which delivered high quality
maps of the inner galaxy in each of its three flights. These data (Figure 1)
show the high infrared luminosity of the inner galaxy, and, together with the
data from the CO survey of the same region by Thaddeus and his colleagues,
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Figure 1. Contour maps of galactic plane emission at 150, 250, and 300 microns
obtained with the 1.2-m diameter balloon-borne telescope developed by the
Infrared Astronomy Group in the High Energy Astrophysics Division. Ex-
tensive diffuse emission is clearly evident, punctuated by discrete sources which
are typically associated with prominent HII regions. Though it is generally
agreed that the diffuse emission is thermal emission from dust, the location
of the dust, whether predominantly associated with molecular, ionized, or
atomic gas remains a question of study. [Figure originally presented by Hauser
et al., 1984, Astrophys. J., 285, 74.]
have allowed systematic study of the distribution and properties of major star-
forming regions in the galaxy [Hauser et al., 1984; Myers et al., 1986].
Subsequent to these flights, the IRAS mission did, of course, initiate the era
of space infrared astronomy in spectacular fashion [Neugebauer et al., 1984;
Hauser, 1986]. We have, for the first time, complete imagery of the sky in
the infrared (Figure 2), including an initial determination of the heretofore
elusive absolute brightness of the sky, and catalogs of hundreds of thousands
of discrete sources, including tens of thousands of extragalactic objects. New
insights and discoveries have emerged in wide ranging astrophysical domains,
from concentrations of dust in the solar system offering clues to the origin
of the interplanetary cloud, to primordial solid material orbiting nearby stars
suggesting early stages of planetary system formation, and to galaxies with
near-quasar luminosity emitting more than 99 % of their energy in the infrared.
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ORIGINAL PAGE IS 
OF POOR QUALITY 
Figure 2. The distribution of 100 micron emission over the full sky as measured 
by IRAS. This Aitoff projection is in galactic coordinates, with the galactic 
center at the center of the projection. The data have been filtered to suppress 
the very large-scale emission, such as that from interplanetary dust. In addi- 
tion to the prominent emission from the galactic plane, here seen all around 
the sky, one sees emission from the nearby molecular cloud regions such as 
Ophiuchus, Orion, and Taurus, large loop structures seen also in HI maps 
of the galaxy, patchy clouds of emission dubbed ‘infrared cirrus’ by the IRAS 
team, and some prominent external galaxies such as the Magellanic Clouds. 
Space-borne cryogenic telescopes are essential to obtaining such a global view 
in the infrared. (Figure prepared from IRAS data by J. Good, JPL.) 
399 
The scientificharvest from IRAS will continue for many yearsas the
astronomicalcommunityscrutinizesandpondersthe data.
WhenNASA decidedto beginseriousstudyof the COBEmission,Frank
McDonaldimmediatelyroseto theoccasionbyurgingthatwetry to hireJohn
Mather,whowasthenaboutto takeapositionat Bell Labs.Thatwasprob-
ablythesecondbestdecisionin theprogram(thefirst beingtodoit, of course!),
becauseJohncouldnotresistthetemptationto pursuethesecretsembedded
in thecosmicbackgroundspectrum,andhasbeenamainstayof theprogram
throughoutitsmanyphases.Theprogramnotonlypromisesuniquelyexciting
science,it hasalso,with thedecisionto build the instrumentsandspacecraft
in-house,turnedout to beamajorcontributorto themaintenanceanddevelop-
mentof Goddard'sengineeringcapabilities.TheCOBEhardwareisnow in
an advancedstageof development,and we eagerlylook forward to the
characterizationof the cosmoswhichthis missionwill provide.
FrankMcDonald'stenureastheofficial championof the infraredastronomy
groupwhichheformedwasrelativelybrief.About threeyearsafterthegroup
wasformed,wewerereorganizedinto the ExtraterrestrialPhysicsDivision
underthe ableguidanceof NormanNess.Frankhimselfsubsequentlyleft
Goddardto takethepositionof ChiefScientistatNASA Headquarters.One
mightsupposethatunderthesecircumstanceshiscontributionsto ourdiscipline
havediminished.I havequiteadifferentview.Boththroughintangibles,such
asthe qualityand spirit whichremainin thegroup whichhecreated,and
in theverytangiblesupportandencouragementheprovidesfor theongoing
programsestablishedunderhis stewardshipand for realizationof thenext
big stepin this field, theSpaceInfraredTelescopeFacility,hecontinuesto
bea major asseto our endeavors.FrankMcDonald'snamemayneverap-
pearon anyof the researchpapersin infraredastronomy;nevertheless,he
is leavinghismarkon thefield no lesssurelythanon themanyotherswhich
hehasinspiredand led.
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REFERENCES
Hauser,M. G. et al., 1984, Astrophys. J., 285, 74.
Hauser, M. G., 1986, "The Cosmos According to IRAS", in Yearbook of
Science and the Future, (Encyclopedia Britannica, Inc.), p. 28.
Myers, P. C. et al., 1986, Astrophys. J., 301, 398.
Neugebauer, G. et al., 1984, Science, 224, 14.
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